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Fri, 26 Jul 2024 16:53:18 -0700 (PDT) Date: Fri, 26 Jul 2024 16:51:29 -0700 In-Reply-To: <20240726235234.228822-1-seanjc@google.com> Mime-Version: 1.0 References: <20240726235234.228822-1-seanjc@google.com> X-Mailer: git-send-email 2.46.0.rc1.232.g9752f9e123-goog Message-ID: <20240726235234.228822-21-seanjc@google.com> Subject: [PATCH v12 20/84] 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, David Matlack , David Stevens X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240726_165319_858717_38702893 X-CRM114-Status: GOOD ( 14.97 ) X-Spam-Score: -9.5 (---------) X-Spam-Report: Spam detection software, running on the system "bombadil.infradead.org", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: 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 [...] Content analysis details: (-9.5 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:114a listed in] [list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM welcome-list 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] -0.0 DKIMWL_WL_MED DKIMwl.org - Medium trust sender X-BeenThere: kvm-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Sender: "kvm-riscv" Errors-To: kvm-riscv-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org 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. 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 f42e030f69a4..a5dcb72bab00 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -273,16 +273,12 @@ enum { READING_SHADOW_PAGE_TABLES, }; -#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= 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 67a50b87bb87..3d717a131906 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3088,7 +3088,7 @@ void kvm_release_pfn(kvm_pfn_t pfn, bool dirty) int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map) { - map->page = KVM_UNMAPPED_PAGE; + map->page = NULL; map->hva = NULL; map->gfn = gfn; @@ -3114,7 +3114,7 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty) if (!map->hva) return; - if (map->page != KVM_UNMAPPED_PAGE) + if (map->page) kunmap(map->page); #ifdef CONFIG_HAS_IOMEM else