Pre-population has been requested several times to mitigate KVM page faults during guest boot or after live migration. It is also required by TDX before filling in the initial guest memory with measured contents; while I am not yet sure that userspace will use this ioctl, if not the code will be used by a TDX-specific ioctl---to pre-populate the SEPT before invoking TDH.MEM.PAGE.ADD or TDH.MR.EXTEND. Compared to Isaku's v2, I have reduced the scope as much as possible: - no vendor-specific hooks - just fail if pre-population is invoked while nested virt is access - just populate page tables for the SMM address space if invoked while SMM is active There are however other changes that affect the userspace API: - struct name changed to `kvm_map_memory` - added support for KVM_CHECK_EXTENSION(KVM_MAP_MEMORY) on the VM file descriptor, which allows to make this ioctl supported only on a subset of VM types vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv - **important**: if EINTR or EAGAIN happens on the first page, it is returned. Otherwise, the ioctl *succeeds* but mapping->size is left nonzero. While this drops the detail as to why the system call was interrupted, it is consistent with other interruptible system calls such as read(). ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Implementation changes: - the test is not x86-specific anymore (though for now only compiled on x86 because no other architectures supports the feature) - instead of using __weak symbols, the code is conditional on a new Kconfig CONFIG_KVM_GENERIC_MAP_MEMORY. This patch series depends on the other pieces that have been applied to the kvm-coco-queue branch (and is present on the branch). Paolo Isaku Yamahata (7): KVM: Document KVM_MAP_MEMORY ioctl KVM: Add KVM_MAP_MEMORY vcpu ioctl to pre-populate guest memory KVM: x86/mmu: Extract __kvm_mmu_do_page_fault() KVM: x86/mmu: Make __kvm_mmu_do_page_fault() return mapped level KVM: x86/mmu: Introduce kvm_tdp_map_page() to populate guest memory KVM: x86: Implement kvm_arch_vcpu_map_memory() KVM: selftests: x86: Add test for KVM_MAP_MEMORY Documentation/virt/kvm/api.rst | 54 +++++++ arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/mmu.h | 3 + arch/x86/kvm/mmu/mmu.c | 32 +++++ arch/x86/kvm/mmu/mmu_internal.h | 42 ++++-- arch/x86/kvm/x86.c | 43 ++++++ include/linux/kvm_host.h | 5 + include/uapi/linux/kvm.h | 10 ++ tools/include/uapi/linux/kvm.h | 8 ++ tools/testing/selftests/kvm/Makefile | 1 + tools/testing/selftests/kvm/map_memory_test.c | 135 ++++++++++++++++++ virt/kvm/Kconfig | 3 + virt/kvm/kvm_main.c | 61 ++++++++ 13 files changed, 384 insertions(+), 14 deletions(-) create mode 100644 tools/testing/selftests/kvm/map_memory_test.c -- 2.43.0
