[PATCH] x86/kvm/hyper-v: tweak HYPERV_CPUID_ENLIGHTMENT_INFO

From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Roman Kagan" <rkagan@virtuozzo.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] x86/kvm/hyper-v: tweak HYPERV_CPUID_ENLIGHTMENT_INFO
Date: Thu, 24 Jan 2019 18:15:16 +0100	[thread overview]
Message-ID: <20190124171516.23626-1-vkuznets@redhat.com> (raw)

We shouldn't probably be suggesting using Enlightened VMCS when it's not
enabled (not supported from guest's point of view). System reset through
synthetic MSR is not recommended neither by genuine Hyper-V nor my QEMU.

Windows seems to be fine either way but let's be consistent.

Fixes: 2bc39970e932 ("x86/kvm/hyper-v: Introduce KVM_GET_SUPPORTED_HV_CPUID")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/hyperv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index ac44a681f065..4730fcaa70cf 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1847,11 +1847,11 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 		case HYPERV_CPUID_ENLIGHTMENT_INFO:
 			ent->eax |= HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED;
 			ent->eax |= HV_X64_APIC_ACCESS_RECOMMENDED;
-			ent->eax |= HV_X64_SYSTEM_RESET_RECOMMENDED;
 			ent->eax |= HV_X64_RELAXED_TIMING_RECOMMENDED;
 			ent->eax |= HV_X64_CLUSTER_IPI_RECOMMENDED;
 			ent->eax |= HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED;
-			ent->eax |= HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
+			if (evmcs_ver)
+				ent->eax |= HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
 
 			/*
 			 * Default number of spinlock retry attempts, matches
-- 
2.20.1

