linux-kernel - [PATCH 16/43] KVM: VMX: Stuff vcpu->arch.apic

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Message-Id: <20210424004645.3950558-17-seanjc@google.com>
Date:   Fri, 23 Apr 2021 17:46:18 -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 16/43] KVM: VMX: Stuff vcpu->arch.apic_base directly at vCPU RESET

Write vcpu->arch.apic_base directly instead of bouncing through
kvm_set_apic_base().  This is a glorified nop, and is a step towards
cleaning up the mess that is local APIC creation.

When using an in-kernel APIC, kvm_create_lapic() explicitly sets
vcpu->arch.apic_base to MSR_IA32_APICBASE_ENABLE to avoid its own
kvm_lapic_set_base() call in kvm_lapic_reset() from triggering state
changes.  That call during RESET exists purely to set apic->base_address
to the default base value.  As a result, by the time VMX gets control,
the only missing piece is the BSP bit being set for the reset BSP.

For a userspace APIC, there are no side effects to process (for the APIC).

In both cases, the call to kvm_update_cpuid_runtime() is a nop because
the vCPU hasn't yet been exposed to userspace, i.e. there can't be any
CPUID entries.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/vmx.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 856aa44b17d5..fa14e9a74b96 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4490,7 +4490,6 @@ static void init_vmcs(struct vcpu_vmx *vmx)
 static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	struct msr_data apic_base_msr;
 	u32 eax, dummy;
 	u64 cr0;

@@ -4511,12 +4510,10 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	kvm_set_cr8(vcpu, 0);

 	if (!init_event) {
-		apic_base_msr.data = APIC_DEFAULT_PHYS_BASE |
-				     MSR_IA32_APICBASE_ENABLE;
+		vcpu->arch.apic_base = APIC_DEFAULT_PHYS_BASE |
+				       MSR_IA32_APICBASE_ENABLE;
 		if (kvm_vcpu_is_reset_bsp(vcpu))
-			apic_base_msr.data |= MSR_IA32_APICBASE_BSP;
-		apic_base_msr.host_initiated = true;
-		kvm_set_apic_base(vcpu, &apic_base_msr);
+			vcpu->arch.apic_base |= MSR_IA32_APICBASE_BSP;
 	}

 	vmx_segment_cache_clear(vmx);
-- 
2.31.1.498.g6c1eba8ee3d-goog