linux-kernel - [PATCH v2 19/30] KVM: x86: hyper-v: Honor HV_STIMER_DIRECT_MODE

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Date:   Fri, 21 May 2021 11:51:53 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 19/30] KVM: x86: hyper-v: Honor HV_STIMER_DIRECT_MODE_AVAILABLE privilege bit

Synthetic timers can only be configured in 'direct' mode when
HV_STIMER_DIRECT_MODE_AVAILABLE bit was exposed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index ec065177531b..12b6803de1b7 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -630,11 +630,17 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
 	union hv_stimer_config new_config = {.as_uint64 = config},
 		old_config = {.as_uint64 = stimer->config.as_uint64};
 	struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 	struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
 
 	if (!synic->active && !host)
 		return 1;
 
+	if (unlikely(!host && hv_vcpu->enforce_cpuid && new_config.direct_mode &&
+		     !(hv_vcpu->cpuid_cache.features_edx &
+		       HV_STIMER_DIRECT_MODE_AVAILABLE)))
+		return 1;
+
 	trace_kvm_hv_stimer_set_config(hv_stimer_to_vcpu(stimer)->vcpu_id,
 				       stimer->index, config, host);
 
-- 
2.31.1