As reported, ever since commit 1013af4f585f ("mm/hugetlb: fix
huge_pmd_unshare() vs GUP-fast race") we can end up in some situations
where we perform so many IPI broadcasts when unsharing hugetlb PMD page
tables that it severely regresses some workloads.
In particular, when we fork()+exit(), or when we munmap() a large
area backed by many shared PMD tables, we perform one IPI broadcast per
unshared PMD table.
There are two optimizations to be had:
(1) When we process (unshare) multiple such PMD tables, such as during
exit(), it is sufficient to send a single IPI broadcast (as long as
we respect locking rules) instead of one per PMD table.
Locking prevents that any of these PMD tables could get reuse before
we drop the lock.
(2) When we are not the last sharer (> 2 users including us), there is
no need to send the IPI broadcast. The shared PMD tables cannot
become exclusive (fully unshared) before an IPI will be broadcasted
by the last sharer.
Concurrent GUP-fast could walk into a PMD table just before we
unshared it. It could then succeed in grabbing a page from the
shared page table even after munmap() etc succeeded (and supressed
an IPI). But there is not difference compared to GUP-fast just
sleeping for a while after grabbing the page and re-enabling IRQs.
Most importantly, GUP-fast will never walk into page tables that are
no-longer shared, because the last sharer will issue an IPI
broadcast.
(if ever required, checking whether the PUD changed in GUP-fast
after grabbing the page like we do in the PTE case could handle
this)
So let's rework PMD sharing TLB flushing + IPI sync to use the mmu_gather
infrastructure so we can implement these optimizations and demystify the
code at least a bit. Extend the mmu_gather infrastructure to be able to
deal with our special hugetlb PMD table sharing implementation.
We'll consolidate the handling for (full) unsharing of PMD tables in
tlb_unshare_pmd_ptdesc() and tlb_flush_unshared_tables(), and track
in "struct mmu_gather" whether we had (full) unsharing of PMD tables.
Because locking is very special (concurrent unsharing+reuse must be
prevented), we disallow deferring flushing to tlb_finish_mmu() and instead
require an explicit earlier call to tlb_flush_unshared_tables().
From hugetlb code, we call huge_pmd_unshare_flush() where we make sure
that the expected lock protecting us from concurrent unsharing+reuse is
still held.
Check with a VM_WARN_ON_ONCE() in tlb_finish_mmu() that
tlb_flush_unshared_tables() was properly called earlier.
Document it all properly.
Notes about tlb_remove_table_sync_one() interaction with unsharing:
There are two fairly tricky things:
(1) tlb_remove_table_sync_one() is a NOP on architectures without
CONFIG_MMU_GATHER_RCU_TABLE_FREE.
Here, the assumption is that the previous TLB flush would send an
IPI to all relevant CPUs. Careful: some architectures like x86 only
send IPIs to all relevant CPUs when tlb->freed_tables is set.
The relevant architectures should be selecting
MMU_GATHER_RCU_TABLE_FREE, but x86 might not do that in stable
kernels and it might have been problematic before this patch.
Also, the arch flushing behavior (independent of IPIs) is different
when tlb->freed_tables is set. Do we have to enlighten them to also
take care of tlb->unshared_tables? So far we didn't care, so
hopefully we are fine. Of course, we could be setting
tlb->freed_tables as well, but that might then unnecessarily flush
too much, because the semantics of tlb->freed_tables are a bit
fuzzy.
This patch changes nothing in this regard.
(2) tlb_remove_table_sync_one() is not a NOP on architectures with
CONFIG_MMU_GATHER_RCU_TABLE_FREE that actually don't need a sync.
Take x86 as an example: in the common case (!pv, !X86_FEATURE_INVLPGB)
we still issue IPIs during TLB flushes and don't actually need the
second tlb_remove_table_sync_one().
This optimized can be implemented on top of this, by checking e.g., in
tlb_remove_table_sync_one() whether we really need IPIs. But as
described in (1), it really must honor tlb->freed_tables then to
send IPIs to all relevant CPUs.
Further note that the ptdesc_pmd_pts_dec() in huge_pmd_share() is not a
concern, as we are holding the i_mmap_lock the whole time, preventing
concurrent unsharing. That ptdesc_pmd_pts_dec() usage will be removed
separately as a cleanup later.
There are plenty more cleanups to be had, but they have to wait until
this is fixed.
Fixes: 1013af4f585f ("mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race")
Reported-by: Uschakow, Stanislav" <suschako(a)amazon.de>
Closes: https://lore.kernel.org/all/4d3878531c76479d9f8ca9789dc6485d@amazon.de/
Tested-by: Laurence Oberman <loberman(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: David Hildenbrand (Red Hat) <david(a)kernel.org>
---
include/asm-generic/tlb.h | 74 ++++++++++++++++++++++-
include/linux/hugetlb.h | 19 +++---
mm/hugetlb.c | 121 ++++++++++++++++++++++----------------
mm/mmu_gather.c | 7 +++
mm/mprotect.c | 2 +-
mm/rmap.c | 25 +++++---
6 files changed, 179 insertions(+), 69 deletions(-)
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 1fff717cae510..706416babb3d6 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -364,6 +364,20 @@ struct mmu_gather {
unsigned int vma_huge : 1;
unsigned int vma_pfn : 1;
+ /*
+ * Did we unshare (unmap) any shared page tables? For now only
+ * used for hugetlb PMD table sharing.
+ */
+ unsigned int unshared_tables : 1;
+
+ /*
+ * Did we unshare any page tables such that they are now exclusive
+ * and could get reused+modified by the new owner? When setting this
+ * flag, "unshared_tables" will be set as well. For now only used
+ * for hugetlb PMD table sharing.
+ */
+ unsigned int fully_unshared_tables : 1;
+
unsigned int batch_count;
#ifndef CONFIG_MMU_GATHER_NO_GATHER
@@ -400,6 +414,7 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
tlb->cleared_pmds = 0;
tlb->cleared_puds = 0;
tlb->cleared_p4ds = 0;
+ tlb->unshared_tables = 0;
/*
* Do not reset mmu_gather::vma_* fields here, we do not
* call into tlb_start_vma() again to set them if there is an
@@ -484,7 +499,7 @@ static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
* these bits.
*/
if (!(tlb->freed_tables || tlb->cleared_ptes || tlb->cleared_pmds ||
- tlb->cleared_puds || tlb->cleared_p4ds))
+ tlb->cleared_puds || tlb->cleared_p4ds || tlb->unshared_tables))
return;
tlb_flush(tlb);
@@ -773,6 +788,63 @@ static inline bool huge_pmd_needs_flush(pmd_t oldpmd, pmd_t newpmd)
}
#endif
+#ifdef CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING
+static inline void tlb_unshare_pmd_ptdesc(struct mmu_gather *tlb, struct ptdesc *pt,
+ unsigned long addr)
+{
+ /*
+ * The caller must make sure that concurrent unsharing + exclusive
+ * reuse is impossible until tlb_flush_unshared_tables() was called.
+ */
+ VM_WARN_ON_ONCE(!ptdesc_pmd_is_shared(pt));
+ ptdesc_pmd_pts_dec(pt);
+
+ /* Clearing a PUD pointing at a PMD table with PMD leaves. */
+ tlb_flush_pmd_range(tlb, addr & PUD_MASK, PUD_SIZE);
+
+ /*
+ * If the page table is now exclusively owned, we fully unshared
+ * a page table.
+ */
+ if (!ptdesc_pmd_is_shared(pt))
+ tlb->fully_unshared_tables = true;
+ tlb->unshared_tables = true;
+}
+
+static inline void tlb_flush_unshared_tables(struct mmu_gather *tlb)
+{
+ /*
+ * As soon as the caller drops locks to allow for reuse of
+ * previously-shared tables, these tables could get modified and
+ * even reused outside of hugetlb context, so we have to make sure that
+ * any page table walkers (incl. TLB, GUP-fast) are aware of that
+ * change.
+ *
+ * Even if we are not fully unsharing a PMD table, we must
+ * flush the TLB for the unsharer now.
+ */
+ if (tlb->unshared_tables)
+ tlb_flush_mmu_tlbonly(tlb);
+
+ /*
+ * Similarly, we must make sure that concurrent GUP-fast will not
+ * walk previously-shared page tables that are getting modified+reused
+ * elsewhere. So broadcast an IPI to wait for any concurrent GUP-fast.
+ *
+ * We only perform this when we are the last sharer of a page table,
+ * as the IPI will reach all CPUs: any GUP-fast.
+ *
+ * Note that on configs where tlb_remove_table_sync_one() is a NOP,
+ * the expectation is that the tlb_flush_mmu_tlbonly() would have issued
+ * required IPIs already for us.
+ */
+ if (tlb->fully_unshared_tables) {
+ tlb_remove_table_sync_one();
+ tlb->fully_unshared_tables = false;
+ }
+}
+#endif /* CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING */
+
#endif /* CONFIG_MMU */
#endif /* _ASM_GENERIC__TLB_H */
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 03c8725efa289..63b248c6bfd47 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -240,8 +240,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
pte_t *huge_pte_offset(struct mm_struct *mm,
unsigned long addr, unsigned long sz);
unsigned long hugetlb_mask_last_page(struct hstate *h);
-int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long addr, pte_t *ptep);
+int huge_pmd_unshare(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep);
+void huge_pmd_unshare_flush(struct mmu_gather *tlb, struct vm_area_struct *vma);
void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end);
@@ -271,7 +272,7 @@ void hugetlb_vma_unlock_write(struct vm_area_struct *vma);
int hugetlb_vma_trylock_write(struct vm_area_struct *vma);
void hugetlb_vma_assert_locked(struct vm_area_struct *vma);
void hugetlb_vma_lock_release(struct kref *kref);
-long hugetlb_change_protection(struct vm_area_struct *vma,
+long hugetlb_change_protection(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long address, unsigned long end, pgprot_t newprot,
unsigned long cp_flags);
void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
@@ -300,13 +301,17 @@ static inline struct address_space *hugetlb_folio_mapping_lock_write(
return NULL;
}
-static inline int huge_pmd_unshare(struct mm_struct *mm,
- struct vm_area_struct *vma,
- unsigned long addr, pte_t *ptep)
+static inline int huge_pmd_unshare(struct mmu_gather *tlb,
+ struct vm_area_struct *vma, unsigned long addr, pte_t *ptep)
{
return 0;
}
+static inline void huge_pmd_unshare_flush(struct mmu_gather *tlb,
+ struct vm_area_struct *vma)
+{
+}
+
static inline void adjust_range_if_pmd_sharing_possible(
struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)
@@ -432,7 +437,7 @@ static inline void move_hugetlb_state(struct folio *old_folio,
{
}
-static inline long hugetlb_change_protection(
+static inline long hugetlb_change_protection(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long address,
unsigned long end, pgprot_t newprot,
unsigned long cp_flags)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3c77cdef12a32..7fef0b94b5d1e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5096,8 +5096,9 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
unsigned long last_addr_mask;
pte_t *src_pte, *dst_pte;
struct mmu_notifier_range range;
- bool shared_pmd = false;
+ struct mmu_gather tlb;
+ tlb_gather_mmu(&tlb, vma->vm_mm);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, old_addr,
old_end);
adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
@@ -5122,12 +5123,12 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
if (huge_pte_none(huge_ptep_get(mm, old_addr, src_pte)))
continue;
- if (huge_pmd_unshare(mm, vma, old_addr, src_pte)) {
- shared_pmd = true;
+ if (huge_pmd_unshare(&tlb, vma, old_addr, src_pte)) {
old_addr |= last_addr_mask;
new_addr |= last_addr_mask;
continue;
}
+ tlb_remove_huge_tlb_entry(h, &tlb, src_pte, old_addr);
dst_pte = huge_pte_alloc(mm, new_vma, new_addr, sz);
if (!dst_pte)
@@ -5136,13 +5137,13 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
move_huge_pte(vma, old_addr, new_addr, src_pte, dst_pte, sz);
}
- if (shared_pmd)
- flush_hugetlb_tlb_range(vma, range.start, range.end);
- else
- flush_hugetlb_tlb_range(vma, old_end - len, old_end);
+ tlb_flush_mmu_tlbonly(&tlb);
+ huge_pmd_unshare_flush(&tlb, vma);
+
mmu_notifier_invalidate_range_end(&range);
i_mmap_unlock_write(mapping);
hugetlb_vma_unlock_write(vma);
+ tlb_finish_mmu(&tlb);
return len + old_addr - old_end;
}
@@ -5161,7 +5162,6 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long sz = huge_page_size(h);
bool adjust_reservation;
unsigned long last_addr_mask;
- bool force_flush = false;
WARN_ON(!is_vm_hugetlb_page(vma));
BUG_ON(start & ~huge_page_mask(h));
@@ -5184,10 +5184,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
}
ptl = huge_pte_lock(h, mm, ptep);
- if (huge_pmd_unshare(mm, vma, address, ptep)) {
+ if (huge_pmd_unshare(tlb, vma, address, ptep)) {
spin_unlock(ptl);
- tlb_flush_pmd_range(tlb, address & PUD_MASK, PUD_SIZE);
- force_flush = true;
address |= last_addr_mask;
continue;
}
@@ -5303,14 +5301,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
}
tlb_end_vma(tlb, vma);
- /*
- * There is nothing protecting a previously-shared page table that we
- * unshared through huge_pmd_unshare() from getting freed after we
- * release i_mmap_rwsem, so flush the TLB now. If huge_pmd_unshare()
- * succeeded, flush the range corresponding to the pud.
- */
- if (force_flush)
- tlb_flush_mmu_tlbonly(tlb);
+ huge_pmd_unshare_flush(tlb, vma);
}
void __hugetlb_zap_begin(struct vm_area_struct *vma,
@@ -6399,7 +6390,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
}
#endif /* CONFIG_USERFAULTFD */
-long hugetlb_change_protection(struct vm_area_struct *vma,
+long hugetlb_change_protection(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long address, unsigned long end,
pgprot_t newprot, unsigned long cp_flags)
{
@@ -6409,7 +6400,6 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
pte_t pte;
struct hstate *h = hstate_vma(vma);
long pages = 0, psize = huge_page_size(h);
- bool shared_pmd = false;
struct mmu_notifier_range range;
unsigned long last_addr_mask;
bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
@@ -6452,7 +6442,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
}
}
ptl = huge_pte_lock(h, mm, ptep);
- if (huge_pmd_unshare(mm, vma, address, ptep)) {
+ if (huge_pmd_unshare(tlb, vma, address, ptep)) {
/*
* When uffd-wp is enabled on the vma, unshare
* shouldn't happen at all. Warn about it if it
@@ -6461,7 +6451,6 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
WARN_ON_ONCE(uffd_wp || uffd_wp_resolve);
pages++;
spin_unlock(ptl);
- shared_pmd = true;
address |= last_addr_mask;
continue;
}
@@ -6522,22 +6511,16 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
pte = huge_pte_clear_uffd_wp(pte);
huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
pages++;
+ tlb_remove_huge_tlb_entry(h, tlb, ptep, address);
}
next:
spin_unlock(ptl);
cond_resched();
}
- /*
- * There is nothing protecting a previously-shared page table that we
- * unshared through huge_pmd_unshare() from getting freed after we
- * release i_mmap_rwsem, so flush the TLB now. If huge_pmd_unshare()
- * succeeded, flush the range corresponding to the pud.
- */
- if (shared_pmd)
- flush_hugetlb_tlb_range(vma, range.start, range.end);
- else
- flush_hugetlb_tlb_range(vma, start, end);
+
+ tlb_flush_mmu_tlbonly(tlb);
+ huge_pmd_unshare_flush(tlb, vma);
/*
* No need to call mmu_notifier_arch_invalidate_secondary_tlbs() we are
* downgrading page table protection not changing it to point to a new
@@ -6904,18 +6887,27 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
return pte;
}
-/*
- * unmap huge page backed by shared pte.
+/**
+ * huge_pmd_unshare - Unmap a pmd table if it is shared by multiple users
+ * @tlb: the current mmu_gather.
+ * @vma: the vma covering the pmd table.
+ * @addr: the address we are trying to unshare.
+ * @ptep: pointer into the (pmd) page table.
+ *
+ * Called with the page table lock held, the i_mmap_rwsem held in write mode
+ * and the hugetlb vma lock held in write mode.
*
- * Called with page table lock held.
+ * Note: The caller must call huge_pmd_unshare_flush() before dropping the
+ * i_mmap_rwsem.
*
- * returns: 1 successfully unmapped a shared pte page
- * 0 the underlying pte page is not shared, or it is the last user
+ * Returns: 1 if it was a shared PMD table and it got unmapped, or 0 if it
+ * was not a shared PMD table.
*/
-int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long addr, pte_t *ptep)
+int huge_pmd_unshare(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep)
{
unsigned long sz = huge_page_size(hstate_vma(vma));
+ struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd = pgd_offset(mm, addr);
p4d_t *p4d = p4d_offset(pgd, addr);
pud_t *pud = pud_offset(p4d, addr);
@@ -6927,18 +6919,36 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
i_mmap_assert_write_locked(vma->vm_file->f_mapping);
hugetlb_vma_assert_locked(vma);
pud_clear(pud);
- /*
- * Once our caller drops the rmap lock, some other process might be
- * using this page table as a normal, non-hugetlb page table.
- * Wait for pending gup_fast() in other threads to finish before letting
- * that happen.
- */
- tlb_remove_table_sync_one();
- ptdesc_pmd_pts_dec(virt_to_ptdesc(ptep));
+
+ tlb_unshare_pmd_ptdesc(tlb, virt_to_ptdesc(ptep), addr);
+
mm_dec_nr_pmds(mm);
return 1;
}
+/*
+ * huge_pmd_unshare_flush - Complete a sequence of huge_pmd_unshare() calls
+ * @tlb: the current mmu_gather.
+ * @vma: the vma covering the pmd table.
+ *
+ * Perform necessary TLB flushes or IPI broadcasts to synchronize PMD table
+ * unsharing with concurrent page table walkers.
+ *
+ * This function must be called after a sequence of huge_pmd_unshare()
+ * calls while still holding the i_mmap_rwsem.
+ */
+void huge_pmd_unshare_flush(struct mmu_gather *tlb, struct vm_area_struct *vma)
+{
+ /*
+ * We must synchronize page table unsharing such that nobody will
+ * try reusing a previously-shared page table while it might still
+ * be in use by previous sharers (TLB, GUP_fast).
+ */
+ i_mmap_assert_write_locked(vma->vm_file->f_mapping);
+
+ tlb_flush_unshared_tables(tlb);
+}
+
#else /* !CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING */
pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
@@ -6947,12 +6957,16 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
return NULL;
}
-int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long addr, pte_t *ptep)
+int huge_pmd_unshare(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep)
{
return 0;
}
+void huge_pmd_unshare_flush(struct mmu_gather *tlb, struct vm_area_struct *vma)
+{
+}
+
void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)
{
@@ -7219,6 +7233,7 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
unsigned long sz = huge_page_size(h);
struct mm_struct *mm = vma->vm_mm;
struct mmu_notifier_range range;
+ struct mmu_gather tlb;
unsigned long address;
spinlock_t *ptl;
pte_t *ptep;
@@ -7229,6 +7244,7 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
if (start >= end)
return;
+ tlb_gather_mmu(&tlb, mm);
flush_cache_range(vma, start, end);
/*
* No need to call adjust_range_if_pmd_sharing_possible(), because
@@ -7248,10 +7264,10 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
if (!ptep)
continue;
ptl = huge_pte_lock(h, mm, ptep);
- huge_pmd_unshare(mm, vma, address, ptep);
+ huge_pmd_unshare(&tlb, vma, address, ptep);
spin_unlock(ptl);
}
- flush_hugetlb_tlb_range(vma, start, end);
+ huge_pmd_unshare_flush(&tlb, vma);
if (take_locks) {
i_mmap_unlock_write(vma->vm_file->f_mapping);
hugetlb_vma_unlock_write(vma);
@@ -7261,6 +7277,7 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
* Documentation/mm/mmu_notifier.rst.
*/
mmu_notifier_invalidate_range_end(&range);
+ tlb_finish_mmu(&tlb);
}
/*
diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
index 247e3f9db6c7a..030a162a263ba 100644
--- a/mm/mmu_gather.c
+++ b/mm/mmu_gather.c
@@ -426,6 +426,7 @@ static void __tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
#endif
tlb->vma_pfn = 0;
+ tlb->fully_unshared_tables = 0;
__tlb_reset_range(tlb);
inc_tlb_flush_pending(tlb->mm);
}
@@ -468,6 +469,12 @@ void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm)
*/
void tlb_finish_mmu(struct mmu_gather *tlb)
{
+ /*
+ * We expect an earlier huge_pmd_unshare_flush() call to sort this out,
+ * due to complicated locking requirements with page table unsharing.
+ */
+ VM_WARN_ON_ONCE(tlb->fully_unshared_tables);
+
/*
* If there are parallel threads are doing PTE changes on same range
* under non-exclusive lock (e.g., mmap_lock read-side) but defer TLB
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 283889e4f1cec..5c330e817129e 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -652,7 +652,7 @@ long change_protection(struct mmu_gather *tlb,
#endif
if (is_vm_hugetlb_page(vma))
- pages = hugetlb_change_protection(vma, start, end, newprot,
+ pages = hugetlb_change_protection(tlb, vma, start, end, newprot,
cp_flags);
else
pages = change_protection_range(tlb, vma, start, end, newprot,
diff --git a/mm/rmap.c b/mm/rmap.c
index 748f48727a162..d6799afe11147 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -76,7 +76,7 @@
#include <linux/mm_inline.h>
#include <linux/oom.h>
-#include <asm/tlbflush.h>
+#include <asm/tlb.h>
#define CREATE_TRACE_POINTS
#include <trace/events/migrate.h>
@@ -2008,13 +2008,17 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
* if unsuccessful.
*/
if (!anon) {
+ struct mmu_gather tlb;
+
VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
if (!hugetlb_vma_trylock_write(vma))
goto walk_abort;
- if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
+
+ tlb_gather_mmu(&tlb, mm);
+ if (huge_pmd_unshare(&tlb, vma, address, pvmw.pte)) {
hugetlb_vma_unlock_write(vma);
- flush_tlb_range(vma,
- range.start, range.end);
+ huge_pmd_unshare_flush(&tlb, vma);
+ tlb_finish_mmu(&tlb);
/*
* The PMD table was unmapped,
* consequently unmapping the folio.
@@ -2022,6 +2026,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
goto walk_done;
}
hugetlb_vma_unlock_write(vma);
+ tlb_finish_mmu(&tlb);
}
pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
if (pte_dirty(pteval))
@@ -2398,17 +2403,20 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
* fail if unsuccessful.
*/
if (!anon) {
+ struct mmu_gather tlb;
+
VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
if (!hugetlb_vma_trylock_write(vma)) {
page_vma_mapped_walk_done(&pvmw);
ret = false;
break;
}
- if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
- hugetlb_vma_unlock_write(vma);
- flush_tlb_range(vma,
- range.start, range.end);
+ tlb_gather_mmu(&tlb, mm);
+ if (huge_pmd_unshare(&tlb, vma, address, pvmw.pte)) {
+ hugetlb_vma_unlock_write(vma);
+ huge_pmd_unshare_flush(&tlb, vma);
+ tlb_finish_mmu(&tlb);
/*
* The PMD table was unmapped,
* consequently unmapping the folio.
@@ -2417,6 +2425,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
break;
}
hugetlb_vma_unlock_write(vma);
+ tlb_finish_mmu(&tlb);
}
/* Nuke the hugetlb page table entry */
pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
--
2.52.0
We switched from (wrongly) using the page count to an independent
shared count. Now, shared page tables have a refcount of 1 (excluding
speculative references) and instead use ptdesc->pt_share_count to
identify sharing.
We didn't convert hugetlb_pmd_shared(), so right now, we would never
detect a shared PMD table as such, because sharing/unsharing no longer
touches the refcount of a PMD table.
Page migration, like mbind() or migrate_pages() would allow for migrating
folios mapped into such shared PMD tables, even though the folios are
not exclusive. In smaps we would account them as "private" although they
are "shared", and we would be wrongly setting the PM_MMAP_EXCLUSIVE in the
pagemap interface.
Fix it by properly using ptdesc_pmd_is_shared() in hugetlb_pmd_shared().
Fixes: 59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count")
Reviewed-by: Rik van Riel <riel(a)surriel.com>
Reviewed-by: Lance Yang <lance.yang(a)linux.dev>
Tested-by: Lance Yang <lance.yang(a)linux.dev>
Reviewed-by: Harry Yoo <harry.yoo(a)oracle.com>
Tested-by: Laurence Oberman <loberman(a)redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Acked-by: Oscar Salvador <osalvador(a)suse.de>
Cc: <stable(a)vger.kernel.org>
Cc: Liu Shixin <liushixin2(a)huawei.com>
Signed-off-by: David Hildenbrand (Red Hat) <david(a)kernel.org>
---
include/linux/hugetlb.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 019a1c5281e4e..03c8725efa289 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1326,7 +1326,7 @@ static inline __init void hugetlb_cma_reserve(int order)
#ifdef CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING
static inline bool hugetlb_pmd_shared(pte_t *pte)
{
- return page_count(virt_to_page(pte)) > 1;
+ return ptdesc_pmd_is_shared(virt_to_ptdesc(pte));
}
#else
static inline bool hugetlb_pmd_shared(pte_t *pte)
--
2.52.0
From: Sam James <sam(a)gentoo.org>
[ Upstream commit 9aeed9041929812a10a6d693af050846942a1d16 ]
Similar in nature to ab107276607af90b13a5994997e19b7b9731e251. glibc-2.42
drops the legacy termio struct, but the ioctls.h header still defines some
TC* constants in terms of termio (via sizeof). Hardcode the values instead.
This fixes building Python for example, which falls over like:
./Modules/termios.c:1119:16: error: invalid application of 'sizeof' to incomplete type 'struct termio'
Link: https://bugs.gentoo.org/961769
Link: https://bugs.gentoo.org/962600
Signed-off-by: Sam James <sam(a)gentoo.org>
Reviewed-by: Magnus Lindholm <linmag7(a)gmail.com>
Link: https://lore.kernel.org/r/6ebd3451908785cad53b50ca6bc46cfe9d6bc03c.17649224…
Signed-off-by: Magnus Lindholm <linmag7(a)gmail.com>
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
LLM Generated explanations, may be completely bogus:
## Analysis Summary
### 1. COMMIT MESSAGE ANALYSIS
This commit addresses a **userspace build failure** caused by glibc-2.42
removing the legacy `struct termio` definition. The kernel's uapi header
`arch/alpha/include/uapi/asm/ioctls.h` uses `sizeof(struct termio)` in
macro expansions, which fails when that struct is undefined.
**Key signals:**
- Links to two real bug reports (Gentoo bugs #961769 and #962600)
- References a prior fix (ab107276607af) for powerpc with the exact same
issue
- Has `Reviewed-by:` tag
- Demonstrates real-world impact: Python build failure
### 2. CODE CHANGE ANALYSIS
**What the change does:**
```c
// Before: Uses sizeof(struct termio) in macro expansion
#define TCGETA _IOR('t', 23, struct termio)
// After: Pre-computed constant
#define TCGETA 0x40127417
```
**Verification of the hardcoded values:**
Looking at `arch/alpha/include/uapi/asm/ioctl.h`, the ioctl encoding on
alpha is:
- `_IOC_SIZESHIFT` = 16, `_IOC_DIRSHIFT` = 29
- `_IOC_READ` = 2, `_IOC_WRITE` = 4
For `TCGETA = _IOR('t', 23, struct termio)`:
- dir=2, type=0x74, nr=0x17, size=18(0x12)
- Result: `(2<<29)|(0x74<<8)|(0x17)|(0x12<<16)` = **0x40127417** ✓
The hardcoded values are mathematically correct.
### 3. CLASSIFICATION
**Category: BUILD FIX**
This falls under the **build fixes** exception category - it's critical
for users who need to build userspace software with modern glibc. Other
architectures (powerpc, sh, xtensa) already have identical fixes in the
tree.
### 4. SCOPE AND RISK ASSESSMENT
- **Lines changed:** 4
- **Files touched:** 1 (alpha-specific uapi header)
- **Risk: EXTREMELY LOW**
- No runtime behavior change - only affects compilation
- The ioctl numbers are identical (pre-computed vs macro-computed)
- Pattern already established in other architectures
### 5. USER IMPACT
- **Affected users:** Anyone on alpha using glibc 2.42+ (e.g., Gentoo
users)
- **Severity:** Critical for affected users - cannot build Python, and
potentially many other programs that use termios
- **Scope:** Limited to alpha architecture, but complete blocker for
those users
### 6. STABILITY INDICATORS
- Has `Reviewed-by:` tag
- Same pattern accepted for powerpc (commit ab107276607af)
- Documented with actual bug reports showing real users affected
- No runtime changes - purely compile-time fix
### 7. DEPENDENCY CHECK
- **No dependencies** - standalone fix
- The affected file exists in all stable trees (uapi header)
- Clean application expected
### Final Assessment
**Pros:**
- Fixes a real, documented build breakage with modern glibc
- Extremely small and localized (4 lines, 1 file)
- Zero runtime risk - mathematically equivalent values
- Established precedent with powerpc fix
- Has review tag and bug report links
**Cons:**
- No explicit `Cc: stable(a)vger.kernel.org` tag
- Alpha is a niche architecture
**Verdict:** This is textbook stable material. It's a build fix that:
1. Is obviously correct (values are mathematically equivalent)
2. Fixes a real bug (complete build failure)
3. Is small and contained (4 lines)
4. Has no runtime risk whatsoever
5. Follows established precedent from other architectures
The lack of a stable tag is not disqualifying - many valid stable
patches don't have it. Build compatibility with modern toolchains is
exactly what stable trees need to maintain.
**YES**
arch/alpha/include/uapi/asm/ioctls.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/alpha/include/uapi/asm/ioctls.h b/arch/alpha/include/uapi/asm/ioctls.h
index 971311605288f..a09d04b49cc65 100644
--- a/arch/alpha/include/uapi/asm/ioctls.h
+++ b/arch/alpha/include/uapi/asm/ioctls.h
@@ -23,10 +23,10 @@
#define TCSETSW _IOW('t', 21, struct termios)
#define TCSETSF _IOW('t', 22, struct termios)
-#define TCGETA _IOR('t', 23, struct termio)
-#define TCSETA _IOW('t', 24, struct termio)
-#define TCSETAW _IOW('t', 25, struct termio)
-#define TCSETAF _IOW('t', 28, struct termio)
+#define TCGETA 0x40127417
+#define TCSETA 0x80127418
+#define TCSETAW 0x80127419
+#define TCSETAF 0x8012741c
#define TCSBRK _IO('t', 29)
#define TCXONC _IO('t', 30)
--
2.51.0
Commit 9a7c987fb92b ("crypto: arm64/ghash - Use API partial block
handling") made ghash_finup() pass the wrong buffer to
ghash_do_simd_update(). As a result, ghash-neon now produces incorrect
outputs when the message length isn't divisible by 16 bytes. Fix this.
(I didn't notice this earlier because this code is reached only on CPUs
that support NEON but not PMULL. I haven't yet found a way to get
qemu-system-aarch64 to emulate that configuration.)
Fixes: 9a7c987fb92b ("crypto: arm64/ghash - Use API partial block handling")
Cc: stable(a)vger.kernel.org
Reported-by: Diederik de Haas <diederik(a)cknow-tech.com>
Closes: https://lore.kernel.org/linux-crypto/DETXT7QI62KE.F3CGH2VWX1SC@cknow-tech.c…
Signed-off-by: Eric Biggers <ebiggers(a)kernel.org>
---
If it's okay, I'd like to just take this via libcrypto-fixes.
arch/arm64/crypto/ghash-ce-glue.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/crypto/ghash-ce-glue.c b/arch/arm64/crypto/ghash-ce-glue.c
index 7951557a285a..ef249d06c92c 100644
--- a/arch/arm64/crypto/ghash-ce-glue.c
+++ b/arch/arm64/crypto/ghash-ce-glue.c
@@ -131,11 +131,11 @@ static int ghash_finup(struct shash_desc *desc, const u8 *src,
if (len) {
u8 buf[GHASH_BLOCK_SIZE] = {};
memcpy(buf, src, len);
- ghash_do_simd_update(1, ctx->digest, src, key, NULL,
+ ghash_do_simd_update(1, ctx->digest, buf, key, NULL,
pmull_ghash_update_p8);
memzero_explicit(buf, sizeof(buf));
}
return ghash_export(desc, dst);
}
base-commit: 7a3984bbd69055898add0fe22445f99435f33450
--
2.52.0
The Dell XPS 13 9350 and XPS 16 9640 both have an upside-down mounted
OV02C10 sensor. This rotation of 180° is reported in neither the SSDB nor
the _PLD for the sensor (both report a rotation of 0°).
Add a DMI quirk mechanism for upside-down sensors and add 2 initial entries
to the DMI quirk list for these 2 laptops.
Note the OV02C10 driver was originally developed on a XPS 16 9640 which
resulted in inverted vflip + hflip settings making it look like the sensor
was upright on the XPS 16 9640 and upside down elsewhere this has been
fixed in commit 69fe27173396 ("media: ov02c10: Fix default vertical flip").
This makes this commit a regression fix since now the video is upside down
on these Dell XPS models where it was not before.
Fixes: d5ebe3f7d13d ("media: ov02c10: Fix default vertical flip")
Cc: stable(a)vger.kernel.org
Reviewed-by: Bryan O'Donoghue <bod(a)kernel.org>
Signed-off-by: Hans de Goede <johannes.goede(a)oss.qualcomm.com>
---
Changes in v2:
- Fix fixes tag to use the correct commit hash
- Drop || COMPILE_TEST from Kconfig to fix compile errors when ACPI is disabled
---
drivers/media/pci/intel/Kconfig | 2 +-
drivers/media/pci/intel/ipu-bridge.c | 29 ++++++++++++++++++++++++++++
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/drivers/media/pci/intel/Kconfig b/drivers/media/pci/intel/Kconfig
index d9fcddce028b..3f14ca110d06 100644
--- a/drivers/media/pci/intel/Kconfig
+++ b/drivers/media/pci/intel/Kconfig
@@ -6,7 +6,7 @@ source "drivers/media/pci/intel/ivsc/Kconfig"
config IPU_BRIDGE
tristate "Intel IPU Bridge"
- depends on ACPI || COMPILE_TEST
+ depends on ACPI
depends on I2C
help
The IPU bridge is a helper library for Intel IPU drivers to
diff --git a/drivers/media/pci/intel/ipu-bridge.c b/drivers/media/pci/intel/ipu-bridge.c
index 58ea01d40c0d..6463b2a47d78 100644
--- a/drivers/media/pci/intel/ipu-bridge.c
+++ b/drivers/media/pci/intel/ipu-bridge.c
@@ -5,6 +5,7 @@
#include <acpi/acpi_bus.h>
#include <linux/cleanup.h>
#include <linux/device.h>
+#include <linux/dmi.h>
#include <linux/i2c.h>
#include <linux/mei_cl_bus.h>
#include <linux/platform_device.h>
@@ -99,6 +100,28 @@ static const struct ipu_sensor_config ipu_supported_sensors[] = {
IPU_SENSOR_CONFIG("XMCC0003", 1, 321468000),
};
+/*
+ * DMI matches for laptops which have their sensor mounted upside-down
+ * without reporting a rotation of 180° in neither the SSDB nor the _PLD.
+ */
+static const struct dmi_system_id upside_down_sensor_dmi_ids[] = {
+ {
+ .matches = {
+ DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+ DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "XPS 13 9350"),
+ },
+ .driver_data = "OVTI02C1",
+ },
+ {
+ .matches = {
+ DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+ DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "XPS 16 9640"),
+ },
+ .driver_data = "OVTI02C1",
+ },
+ {} /* Terminating entry */
+};
+
static const struct ipu_property_names prop_names = {
.clock_frequency = "clock-frequency",
.rotation = "rotation",
@@ -249,6 +272,12 @@ static int ipu_bridge_read_acpi_buffer(struct acpi_device *adev, char *id,
static u32 ipu_bridge_parse_rotation(struct acpi_device *adev,
struct ipu_sensor_ssdb *ssdb)
{
+ const struct dmi_system_id *dmi_id;
+
+ dmi_id = dmi_first_match(upside_down_sensor_dmi_ids);
+ if (dmi_id && acpi_dev_hid_match(adev, dmi_id->driver_data))
+ return 180;
+
switch (ssdb->degree) {
case IPU_SENSOR_ROTATION_NORMAL:
return 0;
--
2.52.0
During sensor calibration I noticed that with the hflip control set to
false/disabled the image was mirrored.
The horizontal flip control is inverted and needs to be set to 1 to not
flip. This is something which seems to be common with various recent
Omnivision sensors, the ov01a10 and ov08x40 also have an inverted
mirror control.
Invert the hflip control to fix the sensor mirroring by default.
Fixes: b7cd2ba3f692 ("media: ov02c10: Support hflip and vflip")
Cc: stable(a)vger.kernel.org
Cc: Sebastian Reichel <sre(a)kernel.org>
Reviewed-by: Bryan O'Donoghue <bod(a)kernel.org>
Signed-off-by: Hans de Goede <johannes.goede(a)oss.qualcomm.com>
---
drivers/media/i2c/ov02c10.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/media/i2c/ov02c10.c b/drivers/media/i2c/ov02c10.c
index 384c2f0b1608..f912ae142040 100644
--- a/drivers/media/i2c/ov02c10.c
+++ b/drivers/media/i2c/ov02c10.c
@@ -170,7 +170,7 @@ static const struct reg_sequence sensor_1928x1092_30fps_setting[] = {
{0x3816, 0x01},
{0x3817, 0x01},
- {0x3820, 0xa0},
+ {0x3820, 0xa8},
{0x3821, 0x00},
{0x3822, 0x80},
{0x3823, 0x08},
@@ -462,9 +462,9 @@ static int ov02c10_set_ctrl(struct v4l2_ctrl *ctrl)
case V4L2_CID_HFLIP:
cci_write(ov02c10->regmap, OV02C10_ISP_X_WIN_CONTROL,
- ctrl->val ? 1 : 2, &ret);
+ ctrl->val ? 2 : 1, &ret);
cci_update_bits(ov02c10->regmap, OV02C10_ROTATE_CONTROL,
- BIT(3), ov02c10->hflip->val << 3, &ret);
+ BIT(3), ctrl->val ? 0 : BIT(3), &ret);
break;
case V4L2_CID_VFLIP:
--
2.52.0