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c=simple/simple; d=arm.com; s=foss; t=1779376541; bh=MNIY+H2hz8eNtjx2NQ8oK9Y7qZVnP9XLnCR/UB41CLM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gemme+ZSaLhd4Tk3MSmYUDcqmIj6z1xhnlwkLRuTm5nUM/ZDUx6VkmyUfM7ZolbPj NBeJX8Ebd5phpr1NQ0osyFWnterTKoFrCzWNmJdA8mz8Os+o04XMj5cGTydavR+U5T cC0ECiFd/6DCP8krzcEyfkEC6BDi3F1/zDtxgHGA= Date: Thu, 21 May 2026 16:15:37 +0100 From: Catalin Marinas To: Zeng Heng Cc: will@kernel.org, akpm@linux-foundation.org, npiggin@gmail.com, aneesh.kumar@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, wangkefeng.wang@huawei.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, David Hildenbrand Subject: Re: [PATCH] arm64: tlb: Flush walk cache when unsharing PMD tables Message-ID: References: <20260521073011.4121277-1-zengheng@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 90F0240004 X-Rspamd-Server: rspam03 X-Stat-Signature: 3dguptszzbhxoatbzi7uciexj11yiqiu X-HE-Tag: 1779376542-573619 X-HE-Meta: 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 CwnjO7Jl mZ8lVySSDdu7HUzygIDswInpBY7IxBAv2hHS40Me+UZH/0qXQasixc+gRVU00q1v74I+NGcplSSdRPptZAwjkN4LYxGsSHL6JQyBhnHNZ/fsphmExNOBP5bJ1fDxwgSUT5u5CQchuOxpYckZ3npQV66rfY6QD8NUIq/EOuOjz14Mp78AF8TUCNeN2M1TdzphF/NFPn7QklIf949NCFaxtvQs7vvPwFh/tFPecgl3hjjsQVRT5jkVhaBNyC+YhzYYZP748463tgCPcHhglEzT1jla+2w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, May 21, 2026 at 04:05:07PM +0100, Catalin Marinas wrote: > + David H. > > On Thu, May 21, 2026 at 03:30:11PM +0800, Zeng Heng wrote: > > From: Zeng Heng > > > > 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 > > The fix looks fine but does it need: > > Fixes: 8ce720d5bd91 ("mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather") > Cc: > > > --- > > arch/arm64/include/asm/tlb.h | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h > > index 10869d7731b8..751bd57bc3ba 100644 > > --- a/arch/arm64/include/asm/tlb.h > > +++ b/arch/arm64/include/asm/tlb.h > > @@ -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); Do we need this as well? diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h index 10869d7731b8..3f4ab38cfd6e 100644 --- a/arch/arm64/include/asm/tlb.h +++ b/arch/arm64/include/asm/tlb.h @@ -24,7 +24,7 @@ static void tlb_flush(struct mmu_gather *tlb); static inline int tlb_get_level(struct mmu_gather *tlb) { /* The TTL field is only valid for the leaf entry. */ - if (tlb->freed_tables) + if (tlb->freed_tables || tlb->unshared_tables) return TLBI_TTL_UNKNOWN; if (tlb->cleared_ptes && !(tlb->cleared_pmds ||