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Thu, 10 Oct 2024 11:25:38 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 10 Oct 2024 11:23:24 -0700 In-Reply-To: <20241010182427.1434605-1-seanjc@google.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Post: List-Subscribe: , , List-Unsubscribe: Mime-Version: 1.0 References: <20241010182427.1434605-1-seanjc@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010182427.1434605-23-seanjc@google.com> Subject: [PATCH v13 22/85] KVM: Use NULL for struct page pointer to indicate mremapped memory From: Sean Christopherson To: 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 , Sean Christopherson Cc: 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, "=?UTF-8?q?Alex=20Benn=C3=A9e?=" , Yan Zhao , David Matlack , David Stevens , Andrew Jones Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Drop yet another unnecessary magic page value from KVM, as there's zero reason to use a poisoned pointer to indicate "no page". If KVM uses a NULL page pointer, the kernel will explode just as quickly as if KVM uses a poisoned pointer. Never mind the fact that such usage would be a blatant and egregious KVM bug. Tested-by: Alex Benn=C3=A9e Signed-off-by: Sean Christopherson --- include/linux/kvm_host.h | 4 ---- virt/kvm/kvm_main.c | 4 ++-- 2 files changed, 2 insertions(+), 6 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index cbc7b9c04c14..e3c01cbbc41a 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -273,16 +273,12 @@ enum { READING_SHADOW_PAGE_TABLES, }; =20 -#define KVM_UNMAPPED_PAGE ((void *) 0x500 + POISON_POINTER_DELTA) - struct kvm_host_map { /* * Only valid if the 'pfn' is managed by the host kernel (i.e. There is * a 'struct page' for it. When using mem=3D kernel parameter some memory * can be used as guest memory but they are not managed by host * kernel). - * If 'pfn' is not managed by the host kernel, this field is - * initialized to KVM_UNMAPPED_PAGE. */ struct page *page; void *hva; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index f1c9a781315c..7acb1a8af2e4 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3067,7 +3067,7 @@ void kvm_release_pfn(kvm_pfn_t pfn, bool dirty) =20 int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *ma= p) { - map->page =3D KVM_UNMAPPED_PAGE; + map->page =3D NULL; map->hva =3D NULL; map->gfn =3D gfn; =20 @@ -3093,7 +3093,7 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm= _host_map *map, bool dirty) if (!map->hva) return; =20 - if (map->page !=3D KVM_UNMAPPED_PAGE) + if (map->page) kunmap(map->page); #ifdef CONFIG_HAS_IOMEM else --=20 2.47.0.rc1.288.g06298d1525-goog