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b=miQzFWbCpnHfvfdQ32bAxe+xMAtmIT0OgKdkBXv2CN6IIPy/P8g86o8G4bASKpFJd YOAiYHfw66IWmD3ezco3eUWkC9CQF91siIROZjHr5m+KepJ6Dte136RqqG2A3/XIU4 U7WGR19JdHQ011rZv4veA5cEP1Ao+KeBVUhFWUvirUVWKp/ywg1FBhbCCB93W/xpQl 9l1WWEr5yDtG4nz0xnrhTOV1P2Qm8vHqy7oY0hBitJIPDLg9whGhxwlr5DntXdSV7s eWxrlrVkNsLM1VnRqalToZ+tzP9Bde92IJP1922rzIefvXlNoBvv6wSuPIFyu+kvGf Vy5M7uVfee2EA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RFC v3 49/88] samples/kvm: Implement lookup_pfn_range provider operation 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-v3-49-8484dde66a7e@google.com> References: <20261106-gmem-alternative-providers-v3-0-8484dde66a7e@google.com> <20261106-gmem-alternative-providers-v3-49-8484dde66a7e@google.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sun, 08 Nov 2026 00:44:11 +0000 X-Stat-Signature: j5psdrhm8ebnw8734ad8du33xf5rm6ge X-Rspamd-Server: rspam01 X-Rspam-User: 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_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: C932C120006 X-HE-Tag: 1794098653-132415 X-HE-Meta: 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 ACCPIpfH 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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: - [Medium] samples/kvm: unexpected -EINVAL from mp_gmem_lookup_pfn_range() past npages -- commit 547b053613c36c4e6a545e75a670dd8b4151e0c0 Author: Ackerley Tng samples/kvm: Implement lookup_pfn_range provider operation This commit implements the .lookup_pfn_range callback in the sample memory provider so that it can act as a PFN-mode provider for guest_memfd. > diff --git a/samples/kvm/memory_provider.c b/samples/kvm/memory_provider.c > index 926f3cf68ed49..7fb7365b65940 100644 > --- a/samples/kvm/memory_provider.c > +++ b/samples/kvm/memory_provider.c > @@ -249,10 +249,34 @@ static int mp_gmem_get_pfn(void *provider, pgoff_t = index, unsigned long *pfn, > return 0; > } > =20 > +static int mp_gmem_lookup_pfn_range(void *provider, pgoff_t index, > + unsigned long *pfn, size_t *nr_pages) > +{ > + struct file *resource_file =3D provider; > + struct mp_info *info =3D resource_file->private_data; > + > + if (index >=3D info->npages) > + return -EINVAL; [Severity: Medium] Does returning -EINVAL when index >=3D info->npages trigger a WARN_ONCE() in kvm_gmem_pfn_reclaim() and kvm_gmem_make_shared()? Neither kvm_gmem_attach_resource() nor mp_gmem_attach() rejects attaching a guest_memfd whose inode size exceeds info->npages << PAGE_SHIFT. When closing such a guest_memfd, kvm_gmem_destroy_inode() -> kvm_gmem_pfn_reclaim() walks up to i_size_read(inode) >> PAGE_SHIFT: virt/kvm/guest_memfd.c:kvm_gmem_pfn_reclaim() { ... r =3D gmem_provider_lookup_pfn_range(gi, index, &pfn, &nr_pages); if (!r || r =3D=3D -ENOENT) { step =3D min_t(size_t, nr_pages, end - index); if (!r) kvm_arch_gmem_reclaim(pfn, step); } else { WARN_ONCE(1, "unexpected lookup_pfn_range error %d at index 0x%lx\n", r, index); } ... } Once index reaches info->npages, returning -EINVAL hits the WARN_ONCE() and falls back to step =3D 1, iterating one page at a time across the remaining unbacked range in an unkillable loop. Should this return -ENOENT with *nr_pages set to cover the unbacked tail (or should mp_gmem_attach() reject oversized guest_memfd inodes)? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261106-gmem-alter= native-providers-v3-0-8484dde66a7e@google.com?part=3D49