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Thu, 22 Feb 2024 08:11:00 -0800 (PST) Date: Thu, 22 Feb 2024 16:10:25 +0000 In-Reply-To: <20240222161047.402609-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240222161047.402609-1-tabba@google.com> X-Mailer: git-send-email 2.44.0.rc1.240.g4c46232300-goog Message-ID: <20240222161047.402609-5-tabba@google.com> Subject: [RFC PATCH v1 04/26] KVM: Don't allow private attribute to be set if mapped by host From: Fuad Tabba To: kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, yu.c.zhang@linux.intel.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" Guest private memory should never be mapped by the host. Therefore, do not allow setting the private attribute to guest memory if that memory is mapped by the host. Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 7 ++++++ virt/kvm/kvm_main.c | 51 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index fad296baa84e..f52d5503ddef 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2408,11 +2408,18 @@ static inline bool kvm_gmem_is_mappable(struct kvm *kvm, gfn_t gfn) return !(kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_NOT_MAPPABLE); } + +bool kvm_is_gmem_mapped(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end); #else static inline bool kvm_gmem_is_mappable(struct kvm *kvm, gfn_t gfn) { return false; } + +static inline bool kvm_is_gmem_mapped(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) +{ + return false; +} #endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM_MAPPABLE */ #endif diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fba4dc6e4107..9f6ff314bda3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2516,6 +2516,48 @@ static __always_inline void kvm_handle_gfn_range(struct kvm *kvm, KVM_MMU_UNLOCK(kvm); } +#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM_MAPPABLE +bool kvm_is_gmem_mapped(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) +{ + struct kvm_memslot_iter iter; + + kvm_for_each_memslot_in_gfn_range(&iter, kvm_memslots(kvm), gfn_start, gfn_end) { + struct kvm_memory_slot *memslot = iter.slot; + gfn_t start, end, i; + + start = max(gfn_start, memslot->base_gfn); + end = min(gfn_end, memslot->base_gfn + memslot->npages); + if (WARN_ON_ONCE(start >= end)) + continue; + + for (i = start; i < end; i++) { + struct page *page; + bool is_mapped; + kvm_pfn_t pfn; + int ret; + + /* + * Check the page_mapcount with the page lock held to + * avoid racing with kvm_gmem_fault(). + */ + ret = kvm_gmem_get_pfn_locked(kvm, memslot, i, &pfn, NULL); + if (WARN_ON_ONCE(ret)) + continue; + + page = pfn_to_page(pfn); + is_mapped = page_mapcount(page); + unlock_page(page); + put_page(page); + + if (is_mapped) + return true; + } + } + + return false; +} +#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM_MAPPABLE */ + static bool kvm_pre_set_memory_attributes(struct kvm *kvm, struct kvm_gfn_range *range) { @@ -2565,6 +2607,15 @@ static int __kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end, if (kvm_range_has_memory_attributes(kvm, start, end, attributes)) goto out_unlock; + if (IS_ENABLED(CONFIG_KVM_GENERIC_PRIVATE_MEM_MAPPABLE) && userspace) { + /* Host-mapped memory cannot be private. */ + if ((attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE) && + kvm_is_gmem_mapped(kvm, start, end)) { + r = -EPERM; + goto out_unlock; + } + } + /* * Reserve memory ahead of time to avoid having to deal with failures * partway through setting the new attributes. -- 2.44.0.rc1.240.g4c46232300-goog