linux-kernel - [PATCH 36/43] KVM: VMX: Remove obsolete MSR bitmap refresh at vCPU RESET/INIT

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Date:   Fri, 23 Apr 2021 17:46:38 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 36/43] KVM: VMX: Remove obsolete MSR bitmap refresh at vCPU RESET/INIT

Remove an unnecessary MSR bitmap refresh during vCPU RESET/INIT.  In both
cases, the MSR bitmap already has the desired values and state.

At RESET, the vCPU is guaranteed to be running with x2APIC disabled, the
x2APIC MSRs are guaranteed to be intercepted due to the MSR bitmap being
initialized to all ones by alloc_loaded_vmcs(), and vmx->msr_bitmap_mode
is guaranteed to be zero, i.e. reflecting x2APIC disabled.

At INIT, the APIC_BASE MSR is not modified, thus there can't be any
change in x2APIC state.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/vmx.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d8afca144e11..acfb87f30979 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4569,9 +4569,6 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	if (kvm_mpx_supported())
 		vmcs_write64(GUEST_BNDCFGS, 0);

-	if (cpu_has_vmx_msr_bitmap())
-		vmx_update_msr_bitmap(&vmx->vcpu);
-
 	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0);  /* 22.2.1 */

 	if (cpu_has_vmx_tpr_shadow() && !init_event) {
-- 
2.31.1.498.g6c1eba8ee3d-goog