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AJvYcCXjJKcM6mpNJfCQqpqTrVSmwfOMdqj7HYJOwMh4FchxxtSu1Q5CyxR82AYeZCd7VnVElYQP4Xc=@lists.linux.dev X-Gm-Message-State: AOJu0YzsIuRRVJqOrPnjwNr9+8fzTd3T45DkmVC4wpGwpkJtef2DfsQV adW5nimUafrTi+dZrDG3Bw5puB6Pjp9aGMrhTJh8EoU2TfND+hsHRjkiW+OgxAi91edmcKA/R/P wmw== X-Google-Smtp-Source: AGHT+IG8guHep8zGOe2nsK6QLt0Shc7PDC8FbYnWdhDsCUpgn83x1Mq6gF7ZIdM6iSjg+GCiMUXCi3Qg1A== X-Received: from wmbeq10.prod.google.com ([2002:a05:600c:848a:b0:456:257a:e323]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3585:b0:456:8eb:a35c with SMTP id 5b1f17b1804b1-45868d6b6d3mr19171885e9.31.1753267635103; Wed, 23 Jul 2025 03:47:15 -0700 (PDT) Date: Wed, 23 Jul 2025 11:46:52 +0100 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.50.1.470.g6ba607880d-goog Message-ID: <20250723104714.1674617-1-tabba@google.com> Subject: [PATCH v16 00/22] KVM: Enable host userspace mapping for guest_memfd-backed memory for non-CoCo 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 Content-Type: text/plain; charset="UTF-8" Main changes since v15 [1]: * Rework and simplify Kconfig selection and dependencies. * Always enable guest_memfd for KVM x86 (64-bit) and arm64, which simplifies the enablement checks. * Based on kvm-x86/next: commit 33f843444e28 ("Merge branch 'vmx'"). This patch series enables host userspace mapping of guest_memfd-backed memory for non-CoCo VMs. This is required for several evolving KVM use cases: * Allows VMMs like Firecracker to run guests entirely backed by guest_memfd [2]. This provides a unified memory management model for both confidential and non-confidential guests, simplifying VMM design. * Enhanced Security via direct map removal: When combined with Patrick's series for direct map removal [3], this provides additional hardening against Spectre-like transient execution attacks by eliminating the need for host kernel direct maps of guest memory. * Lays the groundwork for *restricted* mmap() support for guest_memfd-backed memory on CoCo platforms [4] that permit in-place sharing of guest memory with the host. Patch breakdown: * Patches 1-9: Primarily infrastructure refactoring, Kconfig cleaning, and renames to decouple guest_memfd from the concept of "private" memory. * Patches 10-11: Add support for the host to map guest_memfd backed memory for non-CoCo VMs, which includes support for mmap() and fault handling. This is gated by a new configuration option, toggled by a new flag, and advertised to userspace by a new capability (introduced in patch 20). * Patches 12-15: Implement x86 guest_memfd mmap support. * Patches 16-19: Implement arm64 guest_memfd mmap support. * Patch 20: Introduce the new capability to advertise this support and update the documentation. * Patches 21-22: Update and expand selftests for guest_memfd to include mmap functionality and improve portability. To test this patch series and boot a guest utilizing the new features, please refer to the instructions in v8 of the series [5]. Note that kvmtool for Linux 6.16 (available at [6]) is required, as the KVM_CAP_GMEM_MMAP capability number has changed, additionally, drop the --sw_protected kvmtool parameter to test with the default VM type. Cheers, /fuad [1] https://lore.kernel.org/all/20250717162731.446579-1-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/ [6] https://android-kvm.googlesource.com/kvmtool/+/refs/heads/tabba/guestmem-basic-6.16 Ackerley Tng (1): KVM: x86/mmu: Rename .private_max_mapping_level() to .gmem_max_mapping_level() Fuad Tabba (15): KVM: Rename CONFIG_KVM_PRIVATE_MEM to CONFIG_KVM_GUEST_MEMFD KVM: Rename CONFIG_KVM_GENERIC_PRIVATE_MEM to CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE 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: x86: Enable KVM_GUEST_MEMFD for all 64-bit builds KVM: guest_memfd: Add plumbing to host to map guest_memfd pages KVM: guest_memfd: Track guest_memfd mmap support in memslot KVM: arm64: Refactor user_mem_abort() KVM: arm64: Handle guest_memfd-backed guest page faults KVM: arm64: nv: Handle VNCR_EL2-triggered faults backed by guest_memfd KVM: arm64: Enable support for guest_memfd backed memory KVM: Allow and advertise support for host mmap() on guest_memfd files KVM: selftests: Do not use hardcoded page sizes in guest_memfd test KVM: selftests: guest_memfd mmap() test when mmap is supported Sean Christopherson (6): KVM: x86: Have all vendor neutral sub-configs depend on KVM_X86, not just KVM KVM: x86: Select KVM_GENERIC_PRIVATE_MEM directly from KVM_SW_PROTECTED_VM KVM: x86: Select TDX's KVM_GENERIC_xxx dependencies iff CONFIG_KVM_INTEL_TDX=y KVM: x86/mmu: Hoist guest_memfd max level/order helpers "up" in mmu.c KVM: x86/mmu: Enforce guest_memfd's max order when recovering hugepages KVM: x86/mmu: Extend guest_memfd's max mapping level to shared mappings Documentation/virt/kvm/api.rst | 9 + arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/mmu.c | 203 ++++++++++++----- arch/arm64/kvm/nested.c | 41 +++- arch/x86/include/asm/kvm-x86-ops.h | 2 +- arch/x86/include/asm/kvm_host.h | 6 +- arch/x86/kvm/Kconfig | 26 ++- arch/x86/kvm/mmu/mmu.c | 143 +++++++----- arch/x86/kvm/mmu/mmu_internal.h | 2 +- arch/x86/kvm/mmu/tdp_mmu.c | 2 +- arch/x86/kvm/svm/sev.c | 6 +- arch/x86/kvm/svm/svm.c | 2 +- arch/x86/kvm/svm/svm.h | 4 +- arch/x86/kvm/vmx/main.c | 7 +- arch/x86/kvm/vmx/tdx.c | 5 +- arch/x86/kvm/vmx/x86_ops.h | 2 +- arch/x86/kvm/x86.c | 11 + include/linux/kvm_host.h | 38 ++-- include/uapi/linux/kvm.h | 2 + tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/guest_memfd_test.c | 205 +++++++++++++++--- virt/kvm/Kconfig | 15 +- virt/kvm/Makefile.kvm | 2 +- virt/kvm/guest_memfd.c | 81 ++++++- virt/kvm/kvm_main.c | 12 +- virt/kvm/kvm_mm.h | 4 +- 26 files changed, 623 insertions(+), 209 deletions(-) base-commit: 33f843444e28920d6e624c6c24637b4bb5d3c8de -- 2.50.1.470.g6ba607880d-goog