Re: [PATCH v4 18/21] kvm: x86: Add support for getting/setting expanded xstate buffer

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On 1/4/22 20:46, Sean Christopherson wrote:
On Wed, Dec 29, 2021, Yang Zhong wrote:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bdf89c28d2ce..76e1941db223 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4296,6 +4296,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
  		else
  			r = 0;
  		break;
+	case KVM_CAP_XSAVE2:
+		r = kvm->vcpus[0]->arch.guest_fpu.uabi_size;

a) This does not compile against kvm/queue.

    arch/x86/kvm/x86.c: In function ‘kvm_vm_ioctl_check_extension’:
    arch/x86/kvm/x86.c:4317:24: error: ‘struct kvm’ has no member named ‘vcpus’
     4317 |                 r = kvm->vcpus[0]->arch.guest_fpu.uabi_size;

b) vcpu0 is not guaranteed to be non-NULL at this point.

Yang, you can post an incremental patch for this. You can use the highest bit of the guest-permitted xcr0 (i.e. the OR of KVM's supported XCR0 an the guest-permitted dynamic features) and pass it to cpuid(0xD).

Paolo




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