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bh=Q7O9TQ82OHo1p5kXqghd2ovKAQGxVssYtzqC81EqQEI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KFzIoCPEPcx3cVuWH0SZMeEuo77BiH520eb+dYLqeaDbD/oRUXkOuPqannRIsIY2W PwaKHVrvBNC0I6regX8avJTj5BiGd1Aj6A7NJVA8/UCd9HTnM2lzMd5teeqs1Cvl3Y Nf0BUfFMD37qrdrXDow+8UloD884B3iKyoK9quVk= Date: Thu, 21 May 2026 16:05:01 +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: <20260521073011.4121277-1-zengheng@huaweicloud.com> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 887F5180016 X-Rspam-User: X-Stat-Signature: 8rm87wmhohu7cox7tby18muukmp4ofqz X-HE-Tag: 1779375906-395851 X-HE-Meta: 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 E2HDzheX u2rhUL0SzNt46IWyjFf0ShSZhWsWzujtGSKp8d+9xkmgBVSV2iiYo3V1OD6AhlPvuJU6NSbKRcZ0qWEl4tfL5PYd1/foDuBwGKJsLasDAndLfmlamuJ9BoAMfsI2T6BB9/dyZA74pVtf66Gw2ePDM9K3NufuO74xg/futRA/TrxsmwcxjIgOfMuzxftsmaeDAvJAoK6kw8Ex7PkA83sRJ+LVkbBygBT8xqXKCwJj0+rsKz7sKPNx+9mvLZGtTxbMDsuuVHqBPHjpRHygsvEzvp+Lmng== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: + 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); > > -- > 2.43.0 -- Catalin