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AJvYcCVynvSegcCm7nDckt7iEsUQnHt65YkjCzDbjwxxtEGwMljvZfR+nGvSPvyhajMSqCGqyoOPtjfbVXcBCxv1@vger.kernel.org X-Gm-Message-State: AOJu0YxQg8PpkijDmwiiszjajTMtAh2XncLPoyQNYu5g3CuWYA+4wMBr L0L43t3JyXU2xkNTJDNe6hEqtyCsbaoIF921Nxe5EPLFaaZyhBXxxMa8rhSIsb1QtLsxguhYkyH 7Vw== X-Google-Smtp-Source: AGHT+IFlDy6s6kQCZomObt0nTeQZmuxDFTFV7AArwjZO0+GiEINiw46lQ2nFqVLQxSki9vjaGD00Noog+g== X-Received: from wmsr8.prod.google.com ([2002:a05:600c:8b08:b0:43d:56fa:9b95]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:45cf:b0:442:cd03:3e2 with SMTP id 5b1f17b1804b1-451f0a650f0mr75236925e9.2.1749137882808; Thu, 05 Jun 2025 08:38:02 -0700 (PDT) Date: Thu, 5 Jun 2025 16:37:42 +0100 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.49.0.1266.g31b7d2e469-goog Message-ID: <20250605153800.557144-1-tabba@google.com> Subject: [PATCH v11 00/18] KVM: Mapping guest_memfd backed memory at the host for software protected VMs 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 Main changes since v10 [1]: - Added bounds checking when faulting a shared page into the host, along with a selftest to verify the check. - Refactored KVM/arm64's handling of guest faults (user_mem_abort()). I've dropped the Reviewed-by tags from "KVM: arm64: Refactor user_mem_abort()..." since it has changed significantly. - Handled nested virtualization in KVM/arm64 when faulting guest_memfd backed pages into the guest. - Addressed various points of feedback from the last revision. - Still based on Linux 6.15 This patch series enables the mapping of guest_memfd backed memory in the host. This is useful for VMMs like Firecracker that aim to run guests entirely backed by guest_memfd [2]. When combined with Patrick's series for direct map removal [3], this provides additional hardening against Spectre-like transient execution attacks. This series also lays the groundwork for restricted mmap() support for guest_memfd backed memory in the host for Confidential Computing platforms that permit in-place sharing of guest memory with the host [4]. Patch breakdown: Patches 1-7: Primarily refactoring and renaming to decouple the concept of guest memory being "private" from it being backed by guest_memfd. Patches 8-9: Add support for in-place shared memory and the ability for the host to map it. This is gated by a new configuration option, toggled by a new flag, and advertised to userspace by a new capability (introduced in patch 16). Patches 10-15: Implement the x86 and arm64 support for this feature. Patch 16: Introduces the new capability to advertise this support and updates the documentation. Patches 17-18: Add and fix selftests for the new functionality. For details on how to test this patch series, and on how to boot a guest that uses the new features, please refer to v8 [5]. Cheers, /fuad [1] https://lore.kernel.org/all/20250527180245.1413463-1-tabba@google.com/ [2] https://github.com/firecracker-microvm/firecracker/tree/feature/secret-hiding [3] https://lore.kernel.org/all/20250221160728.1584559-1-roypat@amazon.co.uk/ [4] https://lore.kernel.org/all/20250328153133.3504118-1-tabba@google.com/ [5] https://lore.kernel.org/all/20250430165655.605595-1-tabba@google.com/ Ackerley Tng (2): KVM: x86/mmu: Handle guest page faults for guest_memfd with shared memory KVM: x86: Consult guest_memfd when computing max_mapping_level Fuad Tabba (16): KVM: Rename CONFIG_KVM_PRIVATE_MEM to CONFIG_KVM_GMEM KVM: Rename CONFIG_KVM_GENERIC_PRIVATE_MEM to CONFIG_KVM_GENERIC_GMEM_POPULATE KVM: Rename kvm_arch_has_private_mem() to kvm_arch_supports_gmem() KVM: x86: Rename kvm->arch.has_private_mem to kvm->arch.supports_gmem KVM: Rename kvm_slot_can_be_private() to kvm_slot_has_gmem() KVM: Fix comments that refer to slots_lock KVM: Fix comment that refers to kvm uapi header path KVM: guest_memfd: Allow host to map guest_memfd pages KVM: guest_memfd: Track shared memory support in memslot KVM: x86: Enable guest_memfd shared memory for SW-protected VMs KVM: arm64: Refactor user_mem_abort() KVM: arm64: Handle guest_memfd-backed guest page faults KVM: arm64: Enable host mapping of shared guest_memfd memory KVM: Introduce the KVM capability KVM_CAP_GMEM_SHARED_MEM KVM: selftests: Don't use hardcoded page sizes in guest_memfd test KVM: selftests: guest_memfd mmap() test when mapping is allowed Documentation/virt/kvm/api.rst | 9 + arch/arm64/include/asm/kvm_host.h | 5 + arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/mmu.c | 200 +++++++++++++---- arch/x86/include/asm/kvm_host.h | 22 +- arch/x86/kvm/Kconfig | 5 +- arch/x86/kvm/mmu/mmu.c | 135 ++++++----- arch/x86/kvm/svm/sev.c | 4 +- arch/x86/kvm/svm/svm.c | 4 +- arch/x86/kvm/x86.c | 4 +- include/linux/kvm_host.h | 80 +++++-- include/uapi/linux/kvm.h | 2 + tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/guest_memfd_test.c | 212 +++++++++++++++--- virt/kvm/Kconfig | 14 +- virt/kvm/Makefile.kvm | 2 +- virt/kvm/guest_memfd.c | 94 +++++++- virt/kvm/kvm_main.c | 16 +- virt/kvm/kvm_mm.h | 4 +- 19 files changed, 645 insertions(+), 169 deletions(-) base-commit: 0ff41df1cb268fc69e703a08a57ee14ae967d0ca