On Wed, Jan 26, 2022 at 10:22:07AM -0500, Paolo Bonzini wrote: > While working on the QEMU support for AMX, I noticed that there is no > equivalent of ARCH_GET_XCOMP_SUPP in the KVM API. This is important > because KVM_GET_SUPPORTED_CPUID is meant to be passed (by simple-minded > VMMs) to KVM_SET_CPUID2, and therefore it cannot include any dynamic > xsave states that have not been enabled. Probing the availability of > dynamic xsave states therefore, requires a new ioctl or arch_prctl. > > In order to avoid moving supported_xcr0 to the kernel from the KVM > module just for this use, and to ensure that the value can only be > probed if/after the KVM module has been loaded, this series goes > for the former option. > > KVM_CHECK_EXTENSION cannot be used because it only has 32 bits of > output; in order to limit the growth of capabilities and ioctls, the > series adds a /dev/kvm variant of KVM_{GET,HAS}_DEVICE_ATTR that > can be used in the future and by other architectures. It then > implements it in x86 with just one group (0) and attribute > (KVM_X86_XCOMP_GUEST_SUPP). > > The corresponding changes to the tests, in patches 1 and 3, are > designed so that the code will be covered (to the possible extent) > even when running the tests on systems that do not support AMX. > However, the patches have not been tested with AMX. > Paolo, thanks for this patchset. I applied this patchset into latest Linux release, and verified it from kvm selftest tool and Qemu side (In order to verify this easily, I reused the older request permission function like kvm selftest did), all work well. thanks! Yang > Thanks, > > Paolo > > > Paolo Bonzini (3): > selftests: kvm: move vm_xsave_req_perm call to amx_test > KVM: x86: add system attribute to retrieve full set of supported xsave > states > selftests: kvm: check dynamic bits against KVM_X86_XCOMP_GUEST_SUPP > > Documentation/virt/kvm/api.rst | 4 +- > arch/x86/include/uapi/asm/kvm.h | 3 ++ > arch/x86/kvm/x86.c | 45 +++++++++++++++++++ > include/uapi/linux/kvm.h | 1 + > tools/arch/x86/include/uapi/asm/kvm.h | 3 ++ > tools/include/uapi/linux/kvm.h | 1 + > .../selftests/kvm/include/kvm_util_base.h | 1 - > .../selftests/kvm/include/x86_64/processor.h | 1 + > tools/testing/selftests/kvm/lib/kvm_util.c | 7 --- > .../selftests/kvm/lib/x86_64/processor.c | 27 ++++++++--- > tools/testing/selftests/kvm/x86_64/amx_test.c | 2 + > 11 files changed, 80 insertions(+), 15 deletions(-) > > -- > 2.31.1