The following commit has been merged into the x86/mm branch of tip:
Commit-ID: 3ef938c3503563bfc2ac15083557f880d29c2e64 Gitweb: https://git.kernel.org/tip/3ef938c3503563bfc2ac15083557f880d29c2e64 Author: Jann Horn jannh@google.com AuthorDate: Fri, 03 Jan 2025 19:39:38 +01:00 Committer: Peter Zijlstra peterz@infradead.org CommitterDate: Mon, 03 Feb 2025 11:46:03 +01:00
x86/mm: Fix flush_tlb_range() when used for zapping normal PMDs
On the following path, flush_tlb_range() can be used for zapping normal PMD entries (PMD entries that point to page tables) together with the PTE entries in the pointed-to page table:
collapse_pte_mapped_thp pmdp_collapse_flush flush_tlb_range
The arm64 version of flush_tlb_range() has a comment describing that it can be used for page table removal, and does not use any last-level invalidation optimizations. Fix the X86 version by making it behave the same way.
Currently, X86 only uses this information for the following two purposes, which I think means the issue doesn't have much impact:
- In native_flush_tlb_multi() for checking if lazy TLB CPUs need to be IPI'd to avoid issues with speculative page table walks. - In Hyper-V TLB paravirtualization, again for lazy TLB stuff.
The patch "x86/mm: only invalidate final translations with INVLPGB" which is currently under review (see https://lore.kernel.org/all/20241230175550.4046587-13-riel@surriel.com/) would probably be making the impact of this a lot worse.
Fixes: 016c4d92cd16 ("x86/mm/tlb: Add freed_tables argument to flush_tlb_mm_range") Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20250103-x86-collapse-flush-fix-v1-1-3c521856cfa6@... --- arch/x86/include/asm/tlbflush.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 02fc2aa..3da6451 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -242,7 +242,7 @@ void flush_tlb_multi(const struct cpumask *cpumask, flush_tlb_mm_range((vma)->vm_mm, start, end, \ ((vma)->vm_flags & VM_HUGETLB) \ ? huge_page_shift(hstate_vma(vma)) \ - : PAGE_SHIFT, false) + : PAGE_SHIFT, true)
extern void flush_tlb_all(void); extern void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,