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KVM: selftests: Load XSAVE state into untouched vCPU during state test

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Expand x86's state test to load XSAVE state into a "dummy" vCPU prior to
KVM_SET_CPUID2, and again with an empty guest CPUID model.  Except for
off-by-default features, i.e. AMX, KVM's ABI for KVM_SET_XSAVE is that
userspace is allowed to load xfeatures so long as they are supported by
the host.  This is a regression test for a combination of KVM bugs where
the state saved by KVM_GET_XSAVE{2} could not be loaded via KVM_SET_XSAVE
if the saved xstate_bv would load guest-unsupported xfeatures.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230928001956.924301-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-09-27 17:19:55 -07:00 committed by Paolo Bonzini
parent 60d351f18f
commit 7770982078
1 changed files with 17 additions and 2 deletions
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19
tools/testing/selftests/kvm/x86_64/state_test.c
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@ -231,9 +231,9 @@ static void __attribute__((__flatten__)) guest_code(void *arg)
int main(int argc, char *argv[])
{
vm_vaddr_t nested_gva = 0;
struct kvm_cpuid2 empty_cpuid = {};
struct kvm_regs regs1, regs2;
struct kvm_vcpu *vcpu;
struct kvm_vcpu *vcpu, *vcpuN;
struct kvm_vm *vm;
struct kvm_x86_state *state;
struct ucall uc;
@ -286,6 +286,21 @@ int main(int argc, char *argv[])
/* Restore state in a new VM. */
vcpu = vm_recreate_with_one_vcpu(vm);
vcpu_load_state(vcpu, state);
/*
* Restore XSAVE state in a dummy vCPU, first without doing
* KVM_SET_CPUID2, and then with an empty guest CPUID. Except
* for off-by-default xfeatures, e.g. AMX, KVM is supposed to
* allow KVM_SET_XSAVE regardless of guest CPUID. Manually
* load only XSAVE state, MSRs in particular have a much more
* convoluted ABI.
*/
vcpuN = __vm_vcpu_add(vm, vcpu->id + 1);
vcpu_xsave_set(vcpuN, state->xsave);
vcpu_init_cpuid(vcpuN, &empty_cpuid);
vcpu_xsave_set(vcpuN, state->xsave);
kvm_x86_state_cleanup(state);
memset(&regs2, 0, sizeof(regs2));