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Commit 95d51d05 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Greg Kroah-Hartman
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KVM: x86: Forbid VMM to set SYNIC/STIMER MSRs when SynIC wasn't activated 



commit b1e34d325397a33d97d845e312d7cf2a8b646b44 upstream.

Setting non-zero values to SYNIC/STIMER MSRs activates certain features,
this should not happen when KVM_CAP_HYPERV_SYNIC{,2} was not activated.

Note, it would've been better to forbid writing anything to SYNIC/STIMER
MSRs, including zeroes, however, at least QEMU tries clearing
HV_X64_MSR_STIMER0_CONFIG without SynIC. HV_X64_MSR_EOM MSR is somewhat
'special' as writing zero there triggers an action, this also should not
happen when SynIC wasn't activated.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220325132140.25650-4-vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5dbb771c

arch/x86/kvm/hyperv.c

+15 −0
Original line number Diff line number Diff line
@@ -244,6 +244,9 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic, 
	case HV_X64_MSR_EOM: {

		int i;



		if (!synic->active)

			break;



		for (i = 0; i < ARRAY_SIZE(synic->sint); i++)

			kvm_hv_notify_acked_sint(vcpu, i);

		break;
@@ -504,6 +507,12 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer) 
static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,

			     bool host)

{

	struct kvm_vcpu *vcpu = stimer_to_vcpu(stimer);

	struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);



	if (!synic->active && (!host || config))

		return 1;



	trace_kvm_hv_stimer_set_config(stimer_to_vcpu(stimer)->vcpu_id,

				       stimer->index, config, host);
@@ -518,6 +527,12 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config, 
static int stimer_set_count(struct kvm_vcpu_hv_stimer *stimer, u64 count,

			    bool host)

{

	struct kvm_vcpu *vcpu = stimer_to_vcpu(stimer);

	struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);



	if (!synic->active && (!host || count))

		return 1;



	trace_kvm_hv_stimer_set_count(stimer_to_vcpu(stimer)->vcpu_id,

				      stimer->index, count, host);