From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794098653; b=Pco7oUrW6BE0UuaHISiRUergs6w64FHRluKFMqSo0Hqpx1y/0U3ER//0EMXsdL/u7+nA jSzMsNldD94TTzwbtS42JrrHbBfwKIYllzx3I0GqooD3nVbh+WZGlx+vlZBVBJw/yLGtH 52nfRIn01oBBK4GSJVI6lE0Zqcf5qI93tsGROzTK9E+cpJwHd6rU9tlUQmEXAqY1eCy78 p6kNeHFl94VBqMGTxJZEnrizLxN4PZsKKUuPH8A9vF2Rl6At0NwtthXvVPqri2OM6KcnD XixuU+IfP8Vhaj+Oi+inkr7syloVne3RrPIHt+3ISViTCByg74Ma6ZHWGx9Yvqxfu6g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794098653; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=UGBKPRzEO0tszR5z3zc5sWYnix5oTgdEyRhav4QwANA=; b=rd8ZklTBIw3B3vg4AYE1NI/JLzk+ZnZXkVSNMtjdqzM38XWU5m8mu0v1414dagRJKHa9 sp6bru/rvk666nihRa7m3yAUUPYLsZbmq4zULwVHPBzIVRWFA8qQnPxGYd7CpnRcMmVMJ B2fd5l/HWK2Hi/6mG15xVwhiMrj3+LoYTfmd27lWczhCQjIZWLNxLrpspa/uw/rM2kd/p g8obqonsoREMbpLcJCvA4oizvNRS3xdNO8LZ8BSGWQi5Zw7R9S2+2225AhE1W0cmiXO2G SzfAFdnt/4mWGSO0zp65Wf4PI7+ngB7zNmf9PCvBxBe3QqXiGGpdMu3AF6yDStFDGdg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=miQzFWbC; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4AB24606A334 for ; Sun, 8 Nov 2026 00:44:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=miQzFWbC Received: by smtp.kernel.org (Postfix) with ESMTPSA id 417FD1F0089F; Sun, 8 Nov 2026 00:44:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794098653; bh=UGBKPRzEO0tszR5z3zc5sWYnix5oTgdEyRhav4QwANA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; 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-Mailing-List: kvm@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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