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b=WLGt33lfQhis85EhMbNynpfjFZNyIwXjFSFdF+pCNdRzkvKA814/rYRLNpHxSnC6F jo+wc9HEpn8HqriJVcmIk8aXetaWaed83RxyOdVgz0WFtLFEOgoeoaE6XiHQmJg7tI m9YUkYcXqahMPm0Z/PBITQlt2exEEtIPGDOW0/bE= Date: Sun, 4 Oct 2026 22:47:39 -0700 From: Andrew Morton To: Lance Yang Cc: dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, riel@surriel.com, linux-kernel@vger.kernel.org, qi.zheng@linux.dev, nadav.amit@gmail.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, brendan.jackman@linux.dev, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com, Manali.Shukla@amd.com, mingo@kernel.org, stable@vger.kernel.org, toshi.kani@hpe.com, david@kernel.org, mikhail.v.gavrilov@gmail.com, pfalcato@suse.de Subject: Re: [PATCH 1/1] x86/mm: fix incomplete page-table invalidation with TCE Message-Id: <20261004224739.e1049f07332d388169f7ef08@linux-foundation.org> In-Reply-To: <20261005052302.43042-1-lance.yang@linux.dev> References: <20261005052302.43042-1-lance.yang@linux.dev> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Stat-Signature: dxneyhcoqa7mz59goqxmnpcyc494ok3f X-Rspam-User: X-Rspamd-Queue-Id: B3BA580008 X-HE-Tag: 1791179261-961372 X-HE-Meta: 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 p0LFRCVz OWXww5JqgTBI8jMzyy3OrxLZF6RYNpbvbBNYe8amki9GojaXscbcvP+57z/3Qnmz+Y2igBRuwQqYvYU059qxeAOMzxODrFpqCyXCXYnJ2gUSDO0R6zSSBYvJcBZhhNj6nRSPlDt1WsYb8qCIGj76X6ujRHoKLWmXNJC9kjmtdJ6ysg/SVc9xVx/lhRnssUifaKsRci7JDENHMsHGfXpH/O2IYGrMhD757XbgUl0F4XrKHdnOz/0k+dpOIsCTSQR0etL9oBLtZ570KDsku52lsfcWkpmVVt3Phoy5H6ymPzYiMjSXDWLg3yF91STok/2ZUsJ41GpgfCvwyZKXwBlO5JQIuPUV2tyAYT+r5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 5 Oct 2026 13:23:02 +0800 Lance Yang wrote: > pud_free_pmd_page() uses a single-address invalidation to flush the > paging-structure caches before freeing the page tables. With AMD TCE > enabled, this only invalidates upper-level entries associated with the > target address. Cached PMD entries for other addresses in the PUD range can > still reference the PTE pages being freed. > > The AMD manual quoted in the commit enabling TCE says these instructions > remove > > "only those upper-level entries that lead to the target PTE in the page > table hierarchy, leaving unrelated upper-level entries intact." > > Even with all PTEs cleared, speculative page walks can cache present PMD > entries after the earlier TLB purge. > > Use a full TLB flush before freeing the page tables on CPUs with TCE. Keep > the single-address invalidation otherwise. > > Fixes: 440a65b7d25f ("x86/mm: Enable AMD translation cache extensions") > Cc: stable@vger.kernel.org Sorry, but my usual complaint applies. Check the first 32 lines of Documentation/process/stable-kernel-rules.rst. They're very simple, I'm sure x86 people can immediately grasp the importance of this change, but nobody else can. This includes -stable maintainers as well as a large number of other downstream users of our work who are wondering "why should I apply this to my kernel". Let's tell them! iow, and not for the first time: when fixing a bug please fully describe the userspace-visible runtime effects of that bug. Thanks.