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. 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 v3->v4: - renamed everything to KVM_PRE_FAULT_MEMORY, KVM_CAP_PRE_FAULT_MEMORY, struct kvm_pre_fault_memory. - renamed base_address field to gpa - merged introduction of kvm_tdp_map_page() and kvm_arch_vcpu_map_memory() in a single patch, moving the latter to mmu.c; did *not* merge them in a single function though - removed EINVAL return code for RET_PF_RETRY, do it in KVM and exit on signal_pending() - return ENOENT for RET_PF_EMULATE - do not document the possibility that different VMs can have different results for KVM_CHECK_EXTENSION(KVM_CAP_PRE_FAULT_MEMORY) - return long from kvm_arch_vcpu_map_memory(), update size and gpa in kvm_vcpu_map_memory() - cover remaining range.size more thoroughly in the selftest v2->v3: - 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 - struct name changed to `kvm_map_memory` - common code has supports 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 - 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(). - 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. Isaku Yamahata (6): KVM: Document KVM_PRE_FAULT_MEMORY ioctl KVM: Add KVM_PRE_FAULT_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: Implement kvm_arch_vcpu_pre_fault_memory() KVM: selftests: x86: Add test for KVM_PRE_FAULT_MEMORY Documentation/virt/kvm/api.rst | 50 ++++++ arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/mmu/mmu.c | 72 +++++++++ arch/x86/kvm/mmu/mmu_internal.h | 42 +++-- arch/x86/kvm/x86.c | 3 + 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 + .../selftests/kvm/pre_fault_memory_test.c | 146 ++++++++++++++++++ virt/kvm/Kconfig | 3 + virt/kvm/kvm_main.c | 63 ++++++++ 12 files changed, 390 insertions(+), 14 deletions(-) create mode 100644 tools/testing/selftests/kvm/pre_fault_memory_test.c -- 2.43.0
