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AJvYcCW23fY16fD6TXxz0COxjG43rMAsc5wn6WP8nQ49HEWRvHkb09NJxoVgnVnl6nh61x4Wppjhlv8=@lists.linux.dev X-Gm-Message-State: AOJu0Yx71+cTWKIkFYpcTZWZxTWbzxcq8jwYEqNTnVjD5Id+IEzF0JJ/ Nyh+Sbb+8eGVeSgstIWN4GGBy3MmKJe6I0N9yC0T2BhyYj8x/Z9GhD9flbsi3QGNeA/VgCN3nR3 e7Q== X-Google-Smtp-Source: AGHT+IEOpTQLWb/W99hYWPydN9AF4WxIXy9RQ1ao2fIs6Oh5u3U5LCTeCP7RQZ+lgMAn59d3H/C1V9UDvQ== X-Received: from wmbhe6.prod.google.com ([2002:a05:600c:5406:b0:453:f28:e99f]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:190e:b0:442:dcdc:41c8 with SMTP id 5b1f17b1804b1-45325965490mr23058795e9.19.1749648833055; Wed, 11 Jun 2025 06:33:53 -0700 (PDT) Date: Wed, 11 Jun 2025 14:33:22 +0100 In-Reply-To: <20250611133330.1514028-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250611133330.1514028-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.rc0.642.g800a2b2222-goog Message-ID: <20250611133330.1514028-11-tabba@google.com> Subject: [PATCH v12 10/18] KVM: x86/mmu: Handle guest page faults for guest_memfd with shared memory From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.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, 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, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" From: Ackerley Tng For memslots backed by guest_memfd with shared mem support, the KVM MMU must always fault in pages from guest_memfd, and not from the host userspace_addr. Update the fault handler to do so. This patch also refactors related function names for accuracy: kvm_mem_is_private() returns true only when the current private/shared state (in the CoCo sense) of the memory is private, and returns false if the current state is shared explicitly or impicitly, e.g., belongs to a non-CoCo VM. kvm_mmu_faultin_pfn_gmem() is updated to indicate that it can be used to fault in not just private memory, but more generally, from guest_memfd. Co-developed-by: David Hildenbrand Signed-off-by: David Hildenbrand Signed-off-by: Ackerley Tng Co-developed-by: Fuad Tabba Signed-off-by: Fuad Tabba --- arch/x86/kvm/mmu/mmu.c | 38 +++++++++++++++++++++++--------------- include/linux/kvm_host.h | 25 +++++++++++++++++++++++-- 2 files changed, 46 insertions(+), 17 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 75b7b02cfcb7..2aab5a00caee 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3291,6 +3291,11 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm, return __kvm_mmu_max_mapping_level(kvm, slot, gfn, PG_LEVEL_NUM, is_private); } +static inline bool fault_from_gmem(struct kvm_page_fault *fault) +{ + return fault->is_private || kvm_gmem_memslot_supports_shared(fault->slot); +} + void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_memory_slot *slot = fault->slot; @@ -4467,21 +4472,25 @@ static inline u8 kvm_max_level_for_order(int order) return PG_LEVEL_4K; } -static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, - u8 max_level, int gmem_order) +static u8 kvm_max_level_for_fault_and_order(struct kvm *kvm, + struct kvm_page_fault *fault, + int order) { - u8 req_max_level; + u8 max_level = fault->max_level; if (max_level == PG_LEVEL_4K) return PG_LEVEL_4K; - max_level = min(kvm_max_level_for_order(gmem_order), max_level); + max_level = min(kvm_max_level_for_order(order), max_level); if (max_level == PG_LEVEL_4K) return PG_LEVEL_4K; - req_max_level = kvm_x86_call(private_max_mapping_level)(kvm, pfn); - if (req_max_level) - max_level = min(max_level, req_max_level); + if (fault->is_private) { + u8 level = kvm_x86_call(private_max_mapping_level)(kvm, fault->pfn); + + if (level) + max_level = min(max_level, level); + } return max_level; } @@ -4493,10 +4502,10 @@ static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu, r == RET_PF_RETRY, fault->map_writable); } -static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu, - struct kvm_page_fault *fault) +static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu, + struct kvm_page_fault *fault) { - int max_order, r; + int gmem_order, r; if (!kvm_slot_has_gmem(fault->slot)) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); @@ -4504,15 +4513,14 @@ static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu, } r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn, - &fault->refcounted_page, &max_order); + &fault->refcounted_page, &gmem_order); if (r) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return r; } fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY); - fault->max_level = kvm_max_private_mapping_level(vcpu->kvm, fault->pfn, - fault->max_level, max_order); + fault->max_level = kvm_max_level_for_fault_and_order(vcpu->kvm, fault, gmem_order); return RET_PF_CONTINUE; } @@ -4522,8 +4530,8 @@ static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, { unsigned int foll = fault->write ? FOLL_WRITE : 0; - if (fault->is_private) - return kvm_mmu_faultin_pfn_private(vcpu, fault); + if (fault_from_gmem(fault)) + return kvm_mmu_faultin_pfn_gmem(vcpu, fault); foll |= FOLL_NOWAIT; fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn, foll, diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index bba7d2c14177..8f7069385189 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2547,10 +2547,31 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm, bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, struct kvm_gfn_range *range); +/* + * Returns true if the given gfn's private/shared status (in the CoCo sense) is + * private. + * + * A return value of false indicates that the gfn is explicitly or implicitly + * shared (i.e., non-CoCo VMs). + */ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) { - return IS_ENABLED(CONFIG_KVM_GMEM) && - kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; + struct kvm_memory_slot *slot; + + if (!IS_ENABLED(CONFIG_KVM_GMEM)) + return false; + + slot = gfn_to_memslot(kvm, gfn); + if (kvm_slot_has_gmem(slot) && kvm_gmem_memslot_supports_shared(slot)) { + /* + * Without in-place conversion support, if a guest_memfd memslot + * supports shared memory, then all the slot's memory is + * considered not private, i.e., implicitly shared. + */ + return false; + } + + return kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; } #else static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) -- 2.50.0.rc0.642.g800a2b2222-goog