linux-kernel - [PATCH 24/43] KVM: nVMX: Don't speculatively write APIC-access page address

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Message-Id: <1560445409-17363-25-git-send-email-pbonzini@redhat.com>
Date:   Thu, 13 Jun 2019 19:03:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        vkuznets@...hat.com
Subject: [PATCH 24/43] KVM: nVMX: Don't speculatively write APIC-access page address

From: Sean Christopherson <sean.j.christopherson@...el.com>

If nested_get_vmcs12_pages() fails to map L1's APIC_ACCESS_ADDR into
L2, then it disables SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES in vmcs02.
In other words, the APIC_ACCESS_ADDR in vmcs02 is guaranteed to be
written with the correct value before being consumed by hardware, drop
the unneessary VMWRITE.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index d055bbc5cbde..a012118e6c8c 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2083,14 +2083,6 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 			vmcs_write16(GUEST_INTR_STATUS,
 				vmcs12->guest_intr_status);
 
-		/*
-		 * Write an illegal value to APIC_ACCESS_ADDR. Later,
-		 * nested_get_vmcs12_pages will either fix it up or
-		 * remove the VM execution control.
-		 */
-		if (exec_control & SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)
-			vmcs_write64(APIC_ACCESS_ADDR, -1ull);
-
 		vmcs_write32(SECONDARY_VM_EXEC_CONTROL, exec_control);
 	}
 
-- 
1.8.3.1