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AJvYcCUXxZeg1SA2QqHHKHE9iNO+VJ838LLpz4ScSZKMdd4LjMGCaUb+uME7ZpHCPkpZXR1hbLeJcvE=@lists.linux.dev X-Gm-Message-State: AOJu0Yx/ta6xZ8uefoc3hPtjB1BeciVry9vsYwdy3hJ0Cr2w2ichE6LP SRr1ZC/0N1pcFiQoT4kBniGLtHg99EU90Yali4kLNc1ccb9hpkYTUlm2lK93nA4xed3ETaI+BTU Lbw== X-Google-Smtp-Source: AGHT+IHEntPmO9DY+DxchMnwOgYv2GREd1oegFwljdQ3Vt27b6YI+20amCtzyHAiGDugFG1DH5Xc3wIVPQ== X-Received: from wmrm6.prod.google.com ([2002:a05:600c:37c6:b0:456:13a2:2e7e]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:8188:b0:456:1923:7549 with SMTP id 5b1f17b1804b1-45634dd8050mr33926905e9.26.1752769666906; Thu, 17 Jul 2025 09:27:46 -0700 (PDT) Date: Thu, 17 Jul 2025 17:27:24 +0100 In-Reply-To: <20250717162731.446579-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250717162731.446579-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250717162731.446579-15-tabba@google.com> Subject: [PATCH v15 14/21] KVM: x86: Enable guest_memfd mmap for default VM type 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" Enable host userspace mmap support for guest_memfd-backed memory when running KVM with the KVM_X86_DEFAULT_VM type: * Define kvm_arch_supports_gmem_mmap() for KVM_X86_DEFAULT_VM: Introduce the architecture-specific kvm_arch_supports_gmem_mmap() macro, specifically enabling mmap support for KVM_X86_DEFAULT_VM instances. This macro, gated by CONFIG_KVM_GMEM_SUPPORTS_MMAP, ensures that only the default VM type can leverage guest_memfd mmap functionality on x86. This explicit enablement prevents CoCo VMs, which use guest_memfd primarily for private memory and rely on hardware-enforced privacy, from accidentally exposing guest memory via host userspace mappings. * Select CONFIG_KVM_GMEM_SUPPORTS_MMAP in KVM_X86: Enable the CONFIG_KVM_GMEM_SUPPORTS_MMAP Kconfig option when KVM_X86 is selected. This ensures that the necessary code for guest_memfd mmap support (introduced earlier) is compiled into the kernel for x86. This Kconfig option acts as a system-wide gate for the guest_memfd mmap capability. It implicitly enables CONFIG_KVM_GMEM, making guest_memfd available, and then layers the mmap capability on top specifically for the default VM. These changes make guest_memfd a more versatile memory backing for standard KVM guests, allowing VMMs to use a unified guest_memfd model for both private (CoCo) and non-private (default) VMs. This is a prerequisite for use cases such as running Firecracker guests entirely backed by guest_memfd and implementing direct map removal for non-CoCo VMs. Acked-by: David Hildenbrand Co-developed-by: Ackerley Tng Signed-off-by: Ackerley Tng Signed-off-by: Fuad Tabba --- arch/x86/include/asm/kvm_host.h | 9 +++++++++ arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/x86.c | 3 ++- 3 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 543d09fd4bca..e1426adfa93e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -2279,9 +2279,18 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, #ifdef CONFIG_KVM_GMEM #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem) #define kvm_arch_supports_gmem(kvm) ((kvm)->arch.supports_gmem) + +/* + * CoCo VMs with hardware support that use guest_memfd only for backing private + * memory, e.g., TDX, cannot use guest_memfd with userspace mapping enabled. + */ +#define kvm_arch_supports_gmem_mmap(kvm) \ + (IS_ENABLED(CONFIG_KVM_GMEM_SUPPORTS_MMAP) && \ + (kvm)->arch.vm_type == KVM_X86_DEFAULT_VM) #else #define kvm_arch_has_private_mem(kvm) false #define kvm_arch_supports_gmem(kvm) false +#define kvm_arch_supports_gmem_mmap(kvm) false #endif #define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state) diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index 12e723bb76cc..4acecfb70811 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -48,6 +48,7 @@ config KVM_X86 select KVM_GENERIC_PRE_FAULT_MEMORY select KVM_GMEM if KVM_SW_PROTECTED_VM select KVM_GENERIC_MEMORY_ATTRIBUTES if KVM_SW_PROTECTED_VM + select KVM_GMEM_SUPPORTS_MMAP if X86_64 select KVM_WERROR if WERROR config KVM diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index adbdc2cc97d4..ca99187a566e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12781,7 +12781,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) kvm->arch.vm_type = type; kvm->arch.has_private_mem = (type == KVM_X86_SW_PROTECTED_VM); - kvm->arch.supports_gmem = (type == KVM_X86_SW_PROTECTED_VM); + kvm->arch.supports_gmem = + type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM; /* Decided by the vendor code for other VM types. */ kvm->arch.pre_fault_allowed = type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM; -- 2.50.0.727.gbf7dc18ff4-goog