[PATCH 5.4 149/154] x86/mm: Fix flush_tlb_range() when used for zapping normal PMDs

Greg Kroah-Hartman
2025-04-08T12:08:57Z

From: Jann Horn <jannh@google.com>

commit 3ef938c3503563bfc2ac15083557f880d29c2e64 upstream.

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@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/tlbflush.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -572,7 +572,7 @@ struct flush_tlb_info {
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,