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Wed, 31 Jul 2024 09:23:35 -0700 (PDT) Received: from draig.lan ([85.9.250.243]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a7acad416basm784769266b.104.2024.07.31.09.23.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jul 2024 09:23:35 -0700 (PDT) Received: from draig (localhost [IPv6:::1]) by draig.lan (Postfix) with ESMTP id 614DC5F8CB; Wed, 31 Jul 2024 17:23:34 +0100 (BST) From: =?utf-8?Q?Alex_Benn=C3=A9e?= To: Sean Christopherson Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens Subject: Re: [PATCH v12 01/84] KVM: arm64: Release pfn, i.e. put page, if copying MTE tags hits ZONE_DEVICE In-Reply-To: <20240726235234.228822-2-seanjc@google.com> (Sean Christopherson's message of "Fri, 26 Jul 2024 16:51:10 -0700") References: <20240726235234.228822-1-seanjc@google.com> <20240726235234.228822-2-seanjc@google.com> Date: Wed, 31 Jul 2024 17:23:34 +0100 Message-ID: <87a5hxfs3d.fsf@draig.linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240731_092338_213291_88FCD958 X-CRM114-Status: GOOD ( 15.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Sean Christopherson writes: > Put the page reference acquired by gfn_to_pfn_prot() if > kvm_vm_ioctl_mte_copy_tags() runs into ZONE_DEVICE memory. KVM's less- > than-stellar heuristics for dealing with pfn-mapped memory means that KVM > can get a page reference to ZONE_DEVICE memory. > > Fixes: f0376edb1ddc ("KVM: arm64: Add ioctl to fetch/store tags in a gues= t") > Signed-off-by: Sean Christopherson > --- > arch/arm64/kvm/guest.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c > index 11098eb7eb44..e1f0ff08836a 100644 > --- a/arch/arm64/kvm/guest.c > +++ b/arch/arm64/kvm/guest.c > @@ -1059,6 +1059,7 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > page =3D pfn_to_online_page(pfn); > if (!page) { > /* Reject ZONE_DEVICE memory */ > + kvm_release_pfn_clean(pfn); I guess this gets renamed later in the series. However my main comment is does lack of page always mean a ZONE_DEVICE? Looking at pfn_to_online_page() I see a bunch of other checks first. Why isn't it that functions responsibility to clean up after itself if its returning NULLs? > ret =3D -EFAULT; > goto out; > } --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro