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FAILED: patch "[PATCH] ksm: use range-walk function to jump over holes in" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x f5548c318d6520d4fa3c5ed6003eeb710763cbc5 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112006-hungrily-cedar-3eeb@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From f5548c318d6520d4fa3c5ed6003eeb710763cbc5 Mon Sep 17 00:00:00 2001 From: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Date: Wed, 22 Oct 2025 12:30:59 -0300 Subject: [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu. Link: https://lkml.kernel.org/r/20251023035841.41406-1-pedrodemargomes@gmail.com Link: https://lkml.kernel.org/r/20251022153059.22763-1-pedrodemargomes@gmail.com Link: https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redha… [1] Fixes: 31dbd01f3143 ("ksm: Kernel SamePage Merging") Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Co-developed-by: David Hildenbrand <david(a)redhat.com> Signed-off-by: David Hildenbrand <david(a)redhat.com> Reported-by: craftfever <craftfever(a)airmail.cc> Closes: https://lkml.kernel.org/r/020cf8de6e773bb78ba7614ef250129f11a63781@murena.io Suggested-by: David Hildenbrand <david(a)redhat.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Chengming Zhou <chengming.zhou(a)linux.dev> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/ksm.c b/mm/ksm.c index 7bc726b50b2f..c4e730409949 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2455,6 +2455,95 @@ static bool should_skip_rmap_item(struct folio *folio, return true; } +struct ksm_next_page_arg { + struct folio *folio; + struct page *page; + unsigned long addr; +}; + +static int ksm_next_page_pmd_entry(pmd_t *pmdp, unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct ksm_next_page_arg *private = walk->private; + struct vm_area_struct *vma = walk->vma; + pte_t *start_ptep = NULL, *ptep, pte; + struct mm_struct *mm = walk->mm; + struct folio *folio; + struct page *page; + spinlock_t *ptl; + pmd_t pmd; + + if (ksm_test_exit(mm)) + return 0; + + cond_resched(); + + pmd = pmdp_get_lockless(pmdp); + if (!pmd_present(pmd)) + return 0; + + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pmd_leaf(pmd)) { + ptl = pmd_lock(mm, pmdp); + pmd = pmdp_get(pmdp); + + if (!pmd_present(pmd)) { + goto not_found_unlock; + } else if (pmd_leaf(pmd)) { + page = vm_normal_page_pmd(vma, addr, pmd); + if (!page) + goto not_found_unlock; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + goto not_found_unlock; + + page += ((addr & (PMD_SIZE - 1)) >> PAGE_SHIFT); + goto found_unlock; + } + spin_unlock(ptl); + } + + start_ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); + if (!start_ptep) + return 0; + + for (ptep = start_ptep; addr < end; ptep++, addr += PAGE_SIZE) { + pte = ptep_get(ptep); + + if (!pte_present(pte)) + continue; + + page = vm_normal_page(vma, addr, pte); + if (!page) + continue; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + continue; + goto found_unlock; + } + +not_found_unlock: + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + return 0; +found_unlock: + folio_get(folio); + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + private->page = page; + private->folio = folio; + private->addr = addr; + return 1; +} + +static struct mm_walk_ops ksm_next_page_ops = { + .pmd_entry = ksm_next_page_pmd_entry, + .walk_lock = PGWALK_RDLOCK, +}; + static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) { struct mm_struct *mm; @@ -2542,21 +2631,27 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) ksm_scan.address = vma->vm_end; while (ksm_scan.address < vma->vm_end) { + struct ksm_next_page_arg ksm_next_page_arg; struct page *tmp_page = NULL; - struct folio_walk fw; struct folio *folio; if (ksm_test_exit(mm)) break; - folio = folio_walk_start(&fw, vma, ksm_scan.address, 0); - if (folio) { - if (!folio_is_zone_device(folio) && - folio_test_anon(folio)) { - folio_get(folio); - tmp_page = fw.page; - } - folio_walk_end(&fw, vma); + int found; + + found = walk_page_range_vma(vma, ksm_scan.address, + vma->vm_end, + &ksm_next_page_ops, + &ksm_next_page_arg); + + if (found > 0) { + folio = ksm_next_page_arg.folio; + tmp_page = ksm_next_page_arg.page; + ksm_scan.address = ksm_next_page_arg.addr; + } else { + VM_WARN_ON_ONCE(found < 0); + ksm_scan.address = vma->vm_end - PAGE_SIZE; } if (tmp_page) {

1 week, 2 days

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FAILED: patch "[PATCH] ksm: use range-walk function to jump over holes in" failed to apply to 5.10-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x f5548c318d6520d4fa3c5ed6003eeb710763cbc5 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112005-turmoil-elsewhere-e83d@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From f5548c318d6520d4fa3c5ed6003eeb710763cbc5 Mon Sep 17 00:00:00 2001 From: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Date: Wed, 22 Oct 2025 12:30:59 -0300 Subject: [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu. Link: https://lkml.kernel.org/r/20251023035841.41406-1-pedrodemargomes@gmail.com Link: https://lkml.kernel.org/r/20251022153059.22763-1-pedrodemargomes@gmail.com Link: https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redha… [1] Fixes: 31dbd01f3143 ("ksm: Kernel SamePage Merging") Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Co-developed-by: David Hildenbrand <david(a)redhat.com> Signed-off-by: David Hildenbrand <david(a)redhat.com> Reported-by: craftfever <craftfever(a)airmail.cc> Closes: https://lkml.kernel.org/r/020cf8de6e773bb78ba7614ef250129f11a63781@murena.io Suggested-by: David Hildenbrand <david(a)redhat.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Chengming Zhou <chengming.zhou(a)linux.dev> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/ksm.c b/mm/ksm.c index 7bc726b50b2f..c4e730409949 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2455,6 +2455,95 @@ static bool should_skip_rmap_item(struct folio *folio, return true; } +struct ksm_next_page_arg { + struct folio *folio; + struct page *page; + unsigned long addr; +}; + +static int ksm_next_page_pmd_entry(pmd_t *pmdp, unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct ksm_next_page_arg *private = walk->private; + struct vm_area_struct *vma = walk->vma; + pte_t *start_ptep = NULL, *ptep, pte; + struct mm_struct *mm = walk->mm; + struct folio *folio; + struct page *page; + spinlock_t *ptl; + pmd_t pmd; + + if (ksm_test_exit(mm)) + return 0; + + cond_resched(); + + pmd = pmdp_get_lockless(pmdp); + if (!pmd_present(pmd)) + return 0; + + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pmd_leaf(pmd)) { + ptl = pmd_lock(mm, pmdp); + pmd = pmdp_get(pmdp); + + if (!pmd_present(pmd)) { + goto not_found_unlock; + } else if (pmd_leaf(pmd)) { + page = vm_normal_page_pmd(vma, addr, pmd); + if (!page) + goto not_found_unlock; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + goto not_found_unlock; + + page += ((addr & (PMD_SIZE - 1)) >> PAGE_SHIFT); + goto found_unlock; + } + spin_unlock(ptl); + } + + start_ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); + if (!start_ptep) + return 0; + + for (ptep = start_ptep; addr < end; ptep++, addr += PAGE_SIZE) { + pte = ptep_get(ptep); + + if (!pte_present(pte)) + continue; + + page = vm_normal_page(vma, addr, pte); + if (!page) + continue; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + continue; + goto found_unlock; + } + +not_found_unlock: + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + return 0; +found_unlock: + folio_get(folio); + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + private->page = page; + private->folio = folio; + private->addr = addr; + return 1; +} + +static struct mm_walk_ops ksm_next_page_ops = { + .pmd_entry = ksm_next_page_pmd_entry, + .walk_lock = PGWALK_RDLOCK, +}; + static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) { struct mm_struct *mm; @@ -2542,21 +2631,27 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) ksm_scan.address = vma->vm_end; while (ksm_scan.address < vma->vm_end) { + struct ksm_next_page_arg ksm_next_page_arg; struct page *tmp_page = NULL; - struct folio_walk fw; struct folio *folio; if (ksm_test_exit(mm)) break; - folio = folio_walk_start(&fw, vma, ksm_scan.address, 0); - if (folio) { - if (!folio_is_zone_device(folio) && - folio_test_anon(folio)) { - folio_get(folio); - tmp_page = fw.page; - } - folio_walk_end(&fw, vma); + int found; + + found = walk_page_range_vma(vma, ksm_scan.address, + vma->vm_end, + &ksm_next_page_ops, + &ksm_next_page_arg); + + if (found > 0) { + folio = ksm_next_page_arg.folio; + tmp_page = ksm_next_page_arg.page; + ksm_scan.address = ksm_next_page_arg.addr; + } else { + VM_WARN_ON_ONCE(found < 0); + ksm_scan.address = vma->vm_end - PAGE_SIZE; } if (tmp_page) {

1 week, 2 days

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FAILED: patch "[PATCH] ksm: use range-walk function to jump over holes in" failed to apply to 5.15-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x f5548c318d6520d4fa3c5ed6003eeb710763cbc5 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112003-afloat-squall-e39d@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From f5548c318d6520d4fa3c5ed6003eeb710763cbc5 Mon Sep 17 00:00:00 2001 From: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Date: Wed, 22 Oct 2025 12:30:59 -0300 Subject: [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu. Link: https://lkml.kernel.org/r/20251023035841.41406-1-pedrodemargomes@gmail.com Link: https://lkml.kernel.org/r/20251022153059.22763-1-pedrodemargomes@gmail.com Link: https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redha… [1] Fixes: 31dbd01f3143 ("ksm: Kernel SamePage Merging") Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Co-developed-by: David Hildenbrand <david(a)redhat.com> Signed-off-by: David Hildenbrand <david(a)redhat.com> Reported-by: craftfever <craftfever(a)airmail.cc> Closes: https://lkml.kernel.org/r/020cf8de6e773bb78ba7614ef250129f11a63781@murena.io Suggested-by: David Hildenbrand <david(a)redhat.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Chengming Zhou <chengming.zhou(a)linux.dev> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/ksm.c b/mm/ksm.c index 7bc726b50b2f..c4e730409949 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2455,6 +2455,95 @@ static bool should_skip_rmap_item(struct folio *folio, return true; } +struct ksm_next_page_arg { + struct folio *folio; + struct page *page; + unsigned long addr; +}; + +static int ksm_next_page_pmd_entry(pmd_t *pmdp, unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct ksm_next_page_arg *private = walk->private; + struct vm_area_struct *vma = walk->vma; + pte_t *start_ptep = NULL, *ptep, pte; + struct mm_struct *mm = walk->mm; + struct folio *folio; + struct page *page; + spinlock_t *ptl; + pmd_t pmd; + + if (ksm_test_exit(mm)) + return 0; + + cond_resched(); + + pmd = pmdp_get_lockless(pmdp); + if (!pmd_present(pmd)) + return 0; + + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pmd_leaf(pmd)) { + ptl = pmd_lock(mm, pmdp); + pmd = pmdp_get(pmdp); + + if (!pmd_present(pmd)) { + goto not_found_unlock; + } else if (pmd_leaf(pmd)) { + page = vm_normal_page_pmd(vma, addr, pmd); + if (!page) + goto not_found_unlock; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + goto not_found_unlock; + + page += ((addr & (PMD_SIZE - 1)) >> PAGE_SHIFT); + goto found_unlock; + } + spin_unlock(ptl); + } + + start_ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); + if (!start_ptep) + return 0; + + for (ptep = start_ptep; addr < end; ptep++, addr += PAGE_SIZE) { + pte = ptep_get(ptep); + + if (!pte_present(pte)) + continue; + + page = vm_normal_page(vma, addr, pte); + if (!page) + continue; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + continue; + goto found_unlock; + } + +not_found_unlock: + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + return 0; +found_unlock: + folio_get(folio); + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + private->page = page; + private->folio = folio; + private->addr = addr; + return 1; +} + +static struct mm_walk_ops ksm_next_page_ops = { + .pmd_entry = ksm_next_page_pmd_entry, + .walk_lock = PGWALK_RDLOCK, +}; + static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) { struct mm_struct *mm; @@ -2542,21 +2631,27 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) ksm_scan.address = vma->vm_end; while (ksm_scan.address < vma->vm_end) { + struct ksm_next_page_arg ksm_next_page_arg; struct page *tmp_page = NULL; - struct folio_walk fw; struct folio *folio; if (ksm_test_exit(mm)) break; - folio = folio_walk_start(&fw, vma, ksm_scan.address, 0); - if (folio) { - if (!folio_is_zone_device(folio) && - folio_test_anon(folio)) { - folio_get(folio); - tmp_page = fw.page; - } - folio_walk_end(&fw, vma); + int found; + + found = walk_page_range_vma(vma, ksm_scan.address, + vma->vm_end, + &ksm_next_page_ops, + &ksm_next_page_arg); + + if (found > 0) { + folio = ksm_next_page_arg.folio; + tmp_page = ksm_next_page_arg.page; + ksm_scan.address = ksm_next_page_arg.addr; + } else { + VM_WARN_ON_ONCE(found < 0); + ksm_scan.address = vma->vm_end - PAGE_SIZE; } if (tmp_page) {

1 week, 2 days

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FAILED: patch "[PATCH] ksm: use range-walk function to jump over holes in" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x f5548c318d6520d4fa3c5ed6003eeb710763cbc5 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112001-kitten-trickily-a02d@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From f5548c318d6520d4fa3c5ed6003eeb710763cbc5 Mon Sep 17 00:00:00 2001 From: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Date: Wed, 22 Oct 2025 12:30:59 -0300 Subject: [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu. Link: https://lkml.kernel.org/r/20251023035841.41406-1-pedrodemargomes@gmail.com Link: https://lkml.kernel.org/r/20251022153059.22763-1-pedrodemargomes@gmail.com Link: https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redha… [1] Fixes: 31dbd01f3143 ("ksm: Kernel SamePage Merging") Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Co-developed-by: David Hildenbrand <david(a)redhat.com> Signed-off-by: David Hildenbrand <david(a)redhat.com> Reported-by: craftfever <craftfever(a)airmail.cc> Closes: https://lkml.kernel.org/r/020cf8de6e773bb78ba7614ef250129f11a63781@murena.io Suggested-by: David Hildenbrand <david(a)redhat.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Chengming Zhou <chengming.zhou(a)linux.dev> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/ksm.c b/mm/ksm.c index 7bc726b50b2f..c4e730409949 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2455,6 +2455,95 @@ static bool should_skip_rmap_item(struct folio *folio, return true; } +struct ksm_next_page_arg { + struct folio *folio; + struct page *page; + unsigned long addr; +}; + +static int ksm_next_page_pmd_entry(pmd_t *pmdp, unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct ksm_next_page_arg *private = walk->private; + struct vm_area_struct *vma = walk->vma; + pte_t *start_ptep = NULL, *ptep, pte; + struct mm_struct *mm = walk->mm; + struct folio *folio; + struct page *page; + spinlock_t *ptl; + pmd_t pmd; + + if (ksm_test_exit(mm)) + return 0; + + cond_resched(); + + pmd = pmdp_get_lockless(pmdp); + if (!pmd_present(pmd)) + return 0; + + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pmd_leaf(pmd)) { + ptl = pmd_lock(mm, pmdp); + pmd = pmdp_get(pmdp); + + if (!pmd_present(pmd)) { + goto not_found_unlock; + } else if (pmd_leaf(pmd)) { + page = vm_normal_page_pmd(vma, addr, pmd); + if (!page) + goto not_found_unlock; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + goto not_found_unlock; + + page += ((addr & (PMD_SIZE - 1)) >> PAGE_SHIFT); + goto found_unlock; + } + spin_unlock(ptl); + } + + start_ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); + if (!start_ptep) + return 0; + + for (ptep = start_ptep; addr < end; ptep++, addr += PAGE_SIZE) { + pte = ptep_get(ptep); + + if (!pte_present(pte)) + continue; + + page = vm_normal_page(vma, addr, pte); + if (!page) + continue; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + continue; + goto found_unlock; + } + +not_found_unlock: + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + return 0; +found_unlock: + folio_get(folio); + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + private->page = page; + private->folio = folio; + private->addr = addr; + return 1; +} + +static struct mm_walk_ops ksm_next_page_ops = { + .pmd_entry = ksm_next_page_pmd_entry, + .walk_lock = PGWALK_RDLOCK, +}; + static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) { struct mm_struct *mm; @@ -2542,21 +2631,27 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) ksm_scan.address = vma->vm_end; while (ksm_scan.address < vma->vm_end) { + struct ksm_next_page_arg ksm_next_page_arg; struct page *tmp_page = NULL; - struct folio_walk fw; struct folio *folio; if (ksm_test_exit(mm)) break; - folio = folio_walk_start(&fw, vma, ksm_scan.address, 0); - if (folio) { - if (!folio_is_zone_device(folio) && - folio_test_anon(folio)) { - folio_get(folio); - tmp_page = fw.page; - } - folio_walk_end(&fw, vma); + int found; + + found = walk_page_range_vma(vma, ksm_scan.address, + vma->vm_end, + &ksm_next_page_ops, + &ksm_next_page_arg); + + if (found > 0) { + folio = ksm_next_page_arg.folio; + tmp_page = ksm_next_page_arg.page; + ksm_scan.address = ksm_next_page_arg.addr; + } else { + VM_WARN_ON_ONCE(found < 0); + ksm_scan.address = vma->vm_end - PAGE_SIZE; } if (tmp_page) {

1 week, 2 days

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FAILED: patch "[PATCH] ksm: use range-walk function to jump over holes in" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x f5548c318d6520d4fa3c5ed6003eeb710763cbc5 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112000-stage-compare-58a2@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From f5548c318d6520d4fa3c5ed6003eeb710763cbc5 Mon Sep 17 00:00:00 2001 From: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Date: Wed, 22 Oct 2025 12:30:59 -0300 Subject: [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu. Link: https://lkml.kernel.org/r/20251023035841.41406-1-pedrodemargomes@gmail.com Link: https://lkml.kernel.org/r/20251022153059.22763-1-pedrodemargomes@gmail.com Link: https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redha… [1] Fixes: 31dbd01f3143 ("ksm: Kernel SamePage Merging") Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes(a)gmail.com> Co-developed-by: David Hildenbrand <david(a)redhat.com> Signed-off-by: David Hildenbrand <david(a)redhat.com> Reported-by: craftfever <craftfever(a)airmail.cc> Closes: https://lkml.kernel.org/r/020cf8de6e773bb78ba7614ef250129f11a63781@murena.io Suggested-by: David Hildenbrand <david(a)redhat.com> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Chengming Zhou <chengming.zhou(a)linux.dev> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/ksm.c b/mm/ksm.c index 7bc726b50b2f..c4e730409949 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2455,6 +2455,95 @@ static bool should_skip_rmap_item(struct folio *folio, return true; } +struct ksm_next_page_arg { + struct folio *folio; + struct page *page; + unsigned long addr; +}; + +static int ksm_next_page_pmd_entry(pmd_t *pmdp, unsigned long addr, unsigned long end, + struct mm_walk *walk) +{ + struct ksm_next_page_arg *private = walk->private; + struct vm_area_struct *vma = walk->vma; + pte_t *start_ptep = NULL, *ptep, pte; + struct mm_struct *mm = walk->mm; + struct folio *folio; + struct page *page; + spinlock_t *ptl; + pmd_t pmd; + + if (ksm_test_exit(mm)) + return 0; + + cond_resched(); + + pmd = pmdp_get_lockless(pmdp); + if (!pmd_present(pmd)) + return 0; + + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pmd_leaf(pmd)) { + ptl = pmd_lock(mm, pmdp); + pmd = pmdp_get(pmdp); + + if (!pmd_present(pmd)) { + goto not_found_unlock; + } else if (pmd_leaf(pmd)) { + page = vm_normal_page_pmd(vma, addr, pmd); + if (!page) + goto not_found_unlock; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + goto not_found_unlock; + + page += ((addr & (PMD_SIZE - 1)) >> PAGE_SHIFT); + goto found_unlock; + } + spin_unlock(ptl); + } + + start_ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); + if (!start_ptep) + return 0; + + for (ptep = start_ptep; addr < end; ptep++, addr += PAGE_SIZE) { + pte = ptep_get(ptep); + + if (!pte_present(pte)) + continue; + + page = vm_normal_page(vma, addr, pte); + if (!page) + continue; + folio = page_folio(page); + + if (folio_is_zone_device(folio) || !folio_test_anon(folio)) + continue; + goto found_unlock; + } + +not_found_unlock: + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + return 0; +found_unlock: + folio_get(folio); + spin_unlock(ptl); + if (start_ptep) + pte_unmap(start_ptep); + private->page = page; + private->folio = folio; + private->addr = addr; + return 1; +} + +static struct mm_walk_ops ksm_next_page_ops = { + .pmd_entry = ksm_next_page_pmd_entry, + .walk_lock = PGWALK_RDLOCK, +}; + static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) { struct mm_struct *mm; @@ -2542,21 +2631,27 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) ksm_scan.address = vma->vm_end; while (ksm_scan.address < vma->vm_end) { + struct ksm_next_page_arg ksm_next_page_arg; struct page *tmp_page = NULL; - struct folio_walk fw; struct folio *folio; if (ksm_test_exit(mm)) break; - folio = folio_walk_start(&fw, vma, ksm_scan.address, 0); - if (folio) { - if (!folio_is_zone_device(folio) && - folio_test_anon(folio)) { - folio_get(folio); - tmp_page = fw.page; - } - folio_walk_end(&fw, vma); + int found; + + found = walk_page_range_vma(vma, ksm_scan.address, + vma->vm_end, + &ksm_next_page_ops, + &ksm_next_page_arg); + + if (found > 0) { + folio = ksm_next_page_arg.folio; + tmp_page = ksm_next_page_arg.page; + ksm_scan.address = ksm_next_page_arg.addr; + } else { + VM_WARN_ON_ONCE(found < 0); + ksm_scan.address = vma->vm_end - PAGE_SIZE; } if (tmp_page) {

1 week, 2 days

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FAILED: patch "[PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112033-jovial-sadden-2c80@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Thu, 16 Oct 2025 11:21:47 -0700 Subject: [PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocode that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". But that's a moot point as the TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as documented in the "Unconditionally Blocked Instructions" section of the TDX-Module base specification. Cc: stable(a)vger.kernel.org Cc: Kai Huang <kai.huang(a)intel.com> Cc: Xiaoyao Li <xiaoyao.li(a)intel.com> Cc: Rick Edgecombe <rick.p.edgecombe(a)intel.com> Cc: Dan Williams <dan.j.williams(a)intel.com> Cc: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Kai Huang <kai.huang(a)intel.com> Reviewed-by: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com> Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e..1baa86dfe029 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 76271962cb70..bcea087b642f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return false; default: return true; } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f87c216d976d..91b6f2f3edc2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6032,6 +6032,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6157,6 +6163,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, };

1 week, 2 days

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FAILED: patch "[PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or" failed to apply to 5.10-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112032-cylinder-overlying-2896@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Thu, 16 Oct 2025 11:21:47 -0700 Subject: [PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocode that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". But that's a moot point as the TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as documented in the "Unconditionally Blocked Instructions" section of the TDX-Module base specification. Cc: stable(a)vger.kernel.org Cc: Kai Huang <kai.huang(a)intel.com> Cc: Xiaoyao Li <xiaoyao.li(a)intel.com> Cc: Rick Edgecombe <rick.p.edgecombe(a)intel.com> Cc: Dan Williams <dan.j.williams(a)intel.com> Cc: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Kai Huang <kai.huang(a)intel.com> Reviewed-by: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com> Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e..1baa86dfe029 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 76271962cb70..bcea087b642f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return false; default: return true; } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f87c216d976d..91b6f2f3edc2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6032,6 +6032,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6157,6 +6163,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, };

1 week, 2 days

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FAILED: patch "[PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or" failed to apply to 5.15-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112031-cod-monsoon-9a49@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Thu, 16 Oct 2025 11:21:47 -0700 Subject: [PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocode that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". But that's a moot point as the TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as documented in the "Unconditionally Blocked Instructions" section of the TDX-Module base specification. Cc: stable(a)vger.kernel.org Cc: Kai Huang <kai.huang(a)intel.com> Cc: Xiaoyao Li <xiaoyao.li(a)intel.com> Cc: Rick Edgecombe <rick.p.edgecombe(a)intel.com> Cc: Dan Williams <dan.j.williams(a)intel.com> Cc: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Kai Huang <kai.huang(a)intel.com> Reviewed-by: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com> Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e..1baa86dfe029 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 76271962cb70..bcea087b642f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return false; default: return true; } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f87c216d976d..91b6f2f3edc2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6032,6 +6032,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6157,6 +6163,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, };

1 week, 2 days

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FAILED: patch "[PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112030-dastardly-prowling-1021@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Thu, 16 Oct 2025 11:21:47 -0700 Subject: [PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocode that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". But that's a moot point as the TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as documented in the "Unconditionally Blocked Instructions" section of the TDX-Module base specification. Cc: stable(a)vger.kernel.org Cc: Kai Huang <kai.huang(a)intel.com> Cc: Xiaoyao Li <xiaoyao.li(a)intel.com> Cc: Rick Edgecombe <rick.p.edgecombe(a)intel.com> Cc: Dan Williams <dan.j.williams(a)intel.com> Cc: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Kai Huang <kai.huang(a)intel.com> Reviewed-by: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com> Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e..1baa86dfe029 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 76271962cb70..bcea087b642f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return false; default: return true; } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f87c216d976d..91b6f2f3edc2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6032,6 +6032,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6157,6 +6163,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, };

1 week, 2 days

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FAILED: patch "[PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025112029-degree-siesta-988c@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Thu, 16 Oct 2025 11:21:47 -0700 Subject: [PATCH] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocode that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". But that's a moot point as the TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as documented in the "Unconditionally Blocked Instructions" section of the TDX-Module base specification. Cc: stable(a)vger.kernel.org Cc: Kai Huang <kai.huang(a)intel.com> Cc: Xiaoyao Li <xiaoyao.li(a)intel.com> Cc: Rick Edgecombe <rick.p.edgecombe(a)intel.com> Cc: Dan Williams <dan.j.williams(a)intel.com> Cc: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Kai Huang <kai.huang(a)intel.com> Reviewed-by: Binbin Wu <binbin.wu(a)linux.intel.com> Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com> Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e..1baa86dfe029 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 76271962cb70..bcea087b642f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return false; default: return true; } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f87c216d976d..91b6f2f3edc2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6032,6 +6032,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6157,6 +6163,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, };

1 week, 2 days

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