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b=NwnEeaMFpDr4HwL0jycs22k5go6EI2HbNKolbEPMKVV/MBMx1SZSnj3QssWkYGf5R Dap/Ofy6yw7+SYqovorn4ZfK/9TZ8Y/N4QsV2lnKLZCx14vRbF/bnBVDQrnaTRJm4C e3z4NpNHyY3gN669yrw6WTN7YThxXClelkxmre26uazpUXCOf5YXHd8nJV7c+JtVxO SC8QCK9J+b0MRxWztmJJXlEW6m2t2vdHSLd5xDmadP0lVP/p1vNgqGt4BCzTvMjKs4 wCEyw6hW2w7OTOGohLpSAvYjrfsx65kxNuJ95NkPpH1kyN5IASsfxJAKHGITkJYlkK vWCtV5OnHCKqg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RFC v3 48/88] samples/kvm: Support dynamic revocation via kvm_gmem_revoke Reply-To: sashiko-reviews@lists.linux.dev To: "Ackerley Tng" , "Alexey Kardashevskiy" , "Aneesh Kumar K.V" , "Christian Brauner" , "David Hildenbrand" , "David Woodhouse" , "Fred Griffoul" , "Jacob Pan" , "Jianxiong Gao" , "John Starks" , "Michael Roth" , "Paolo Bonzini" , "Samiullah Khawaja" , "Sean Christopherson" , "Suzuki K Poulose" , "Tarun Sahu" , "Vishal Annapurve" , "Xu Yilun" , "Fuad Tabba" Cc: kvm@vger.kernel.org, linux-mm@kvack.org In-Reply-To: <20261106-gmem-alternative-providers-v3-48-8484dde66a7e@google.com> References: <20261106-gmem-alternative-providers-v3-0-8484dde66a7e@google.com> <20261106-gmem-alternative-providers-v3-48-8484dde66a7e@google.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sun, 08 Nov 2026 00:44:10 +0000 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8D1AA180002 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: 3h6hnckt8bwgn1jfhk1gfimxheeju8a7 X-Rspam-User: X-HE-Tag: 1794098652-135482 X-HE-Meta: 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 PKfq5XRX 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue to consider: - [Low] samples/kvm: stale identifier names and patch references in commit message -- commit 42b1d24c6caccfeaf35dd92048463c002a041484 Author: Ackerley Tng > samples/kvm: Support dynamic revocation via kvm_gmem_revoke > > Support dynamic revocation in the sample memory provider module by > calling kvm_gmem_revoke() when pages are marked absent via > MPS_SET_PRESENT. > > Note down the attaching gmem inode during .attach() and disallow double > attachment to the same provider file. > > Clear the revoked pages after kvm_gmem_revoke() using mps_zero_range() > to ensure that stale data is wiped and cannot be observed when pages are > later marked present or reused. > > Regarding locking and ordering: > - In mps_set_present(), mark the absent bitmap first before revoking so > any concurrent page fault immediately sees the page as absent and > rejects the lookup with -EFAULT. > - kvm_gmem_revoke() is called under info->lock to fully serialize > MPS_SET_PRESENT operations against each other and prevent races > between marking pages absent and present. > - The PFN passed to kvm_gmem_revoke() is derived from info->base_pfn + > start. The mapping between page index and physical PFN is static and > immutable for the lifetime of the provider file, ensuring that the > pfn mapping remains completely stable across the revoke call. > - Passing pfn directly to kvm_gmem_revoke() allows guest_memfd to > reclaim the physical range directly without calling back into the > provider. This keeps the lock hierarchy strictly top-down (info->lock > -> filemap_invalidate_lock -> mmu_lock) with no callbacks or deadlocks. > > For now, nothing needs to be done when setting a page present, since users > should (re-)fault and (re-)obtain the PFN via .get_pfn(), to be added in a > later patch. > > For users that don't support faulting, like the IOMMU, the counterpart to > kvm_gmem_revoke() will be made available for the first user to indicate > that the memory is now available. guest_memfd should then do the page tab= le > mappings as necessary, based on the shared/private status. > > Signed-off-by: Ackerley Tng [Severity: Low] This isn't a bug, but the commit message has a few stale references from an earlier version of the series: - MPS_SET_PRESENT, mps_zero_range(), and mps_set_present() were renamed to MP_SET_PRESENT, mp_zero_range(), and mp_set_present(). - Recording info->gmem_inode in .attach() and disallowing double attachment was already done in commit "samples/kvm: Implement attach and release provider ops in sample provider", not in this patch. - .get_pfn() was already added earlier in the series in commit "samples/kvm: Implement get_pfn provider operation", rather than in a later patch. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261106-gmem-alter= native-providers-v3-0-8484dde66a7e@google.com?part=3D48