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arm64: tlb: Flush walk cache when unsharing PMD tables

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When huge_pmd_unshare() is called to unshare a PMD table, the
tlb_unshare_pmd_ptdesc() function sets tlb->unshared_tables=true
but the aarch64 tlb_flush() only checked tlb->freed_tables to
determine whether to use TLBF_NONE (vae1is, invalidates walk
cache) or TLBF_NOWALKCACHE (vale1is, leaf-only).

This caused the stale PMD page table entry to remain in the walk cache
after unshare, potentially leading to incorrect page table walks.

Fix by including unshared_tables in the check, so that when
unsharing tables, TLBF_NONE is used and the walk cache is properly
invalidated.

Here is the detailed distinction between vae1is and vale1is:

| Instruction Combination  | Actual Invalidation Scope                         |
| ------------------------ | --------------------------------------------------|
| `VAE1IS`  + TTL=`0`      | All entries at all levels (full invalidation)     |
| `VAE1IS`  + TTL=`2` (L2) | Non-leaf at Level 0/1 + leaf at Level 2           |
| `VALE1IS` + TTL=`0`      | Leaf entries at all levels (non-leaf not cleared) |
| `VALE1IS` + TTL=`2` (L2) | Leaf entry at Level 2 only                        |

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Fixes: 8ce720d5bd ("mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather")
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Zeng Heng 2026-05-21 15:30:11 +08:00 committed by Catalin Marinas
parent 2ccd8ff980
commit c2ff4764e0
1 changed files with 2 additions and 1 deletions
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3
arch/arm64/include/asm/tlb.h
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@ -53,7 +53,8 @@ static inline int tlb_get_level(struct mmu_gather *tlb)
static inline void tlb_flush(struct mmu_gather *tlb)
{
struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);
tlbf_t flags = tlb->freed_tables ? TLBF_NONE : TLBF_NOWALKCACHE;
tlbf_t flags = (tlb->freed_tables || tlb->unshared_tables) ?
TLBF_NONE : TLBF_NOWALKCACHE;
unsigned long stride = tlb_get_unmap_size(tlb);
int tlb_level = tlb_get_level(tlb);