[RFC PATCH 48/55] KVM: x86: hyperv: Advertise XMM fast hypercall output

[David Woodhouse]

From: David Woodhouse <dwmw@xxxxxxxxxxxx>

The Hyper-V VSM register hypercalls return data in XMM registers when
the guest uses their fast forms, and the userspace handler answering
them writes those registers through the vCPU FPU state. Report
HV_X64_HYPERCALL_XMM_OUTPUT_AVAILABLE in KVM_GET_SUPPORTED_HV_CPUID so
the VMM can expose it; the reference hypervisor advertises it, and the
Windows secure kernel only uses the fast forms when it is present.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Assisted-by: LLM
---
 arch/x86/kvm/hyperv.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 02866b9b7e9b..dbe1b83c1f28 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -3751,6 +3751,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 			ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS;
 
 			ent->edx |= HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE;
+			ent->edx |= HV_X64_HYPERCALL_XMM_OUTPUT_AVAILABLE;
 			ent->edx |= HV_FEATURE_FREQUENCY_MSRS_AVAILABLE;
 			ent->edx |= HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
 
-- 
2.50.1