linux-kernel - [PATCH] KVM: x86: do not reset microcode version on INIT or RESET

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Message-Id: <1581444279-10033-1-git-send-email-pbonzini@redhat.com>
Date:   Tue, 11 Feb 2020 19:04:39 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH] KVM: x86: do not reset microcode version on INIT or RESET

The microcode version should be set just once, since it is essentially
a CPU feature; so do it on vCPU creation rather than reset.

Userspace can tie the fix to the availability of MSR_IA32_UCODE_REV in
the list of emulated MSRs.

Reported-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm.c     | 2 +-
 arch/x86/kvm/vmx/vmx.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a7e63b613837..280f6d024e84 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2185,7 +2185,6 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	u32 dummy;
 	u32 eax = 1;
 
-	vcpu->arch.microcode_version = 0x01000065;
 	svm->spec_ctrl = 0;
 	svm->virt_spec_ctrl = 0;
 
@@ -2276,6 +2275,7 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 	init_vmcb(svm);
 
 	svm_init_osvw(vcpu);
+	vcpu->arch.microcode_version = 0x01000065;
 
 	return 0;
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9a6664886f2e..d625b4b0e7b4 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4238,7 +4238,6 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 
 	vmx->msr_ia32_umwait_control = 0;
 
-	vcpu->arch.microcode_version = 0x100000000ULL;
 	vmx->vcpu.arch.regs[VCPU_REGS_RDX] = get_rdx_init_val();
 	vmx->hv_deadline_tsc = -1;
 	kvm_set_cr8(vcpu, 0);
@@ -6763,6 +6762,7 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
 	vmx->nested.posted_intr_nv = -1;
 	vmx->nested.current_vmptr = -1ull;
 
+	vcpu->arch.microcode_version = 0x100000000ULL;
 	vmx->msr_ia32_feature_control_valid_bits = FEAT_CTL_LOCKED;
 
 	/*
-- 
1.8.3.1