[PATCH 10/13] KVM: nVMX: Preset *DT exiting in vmcs02 when emulating UMIP

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KVM dynamically toggles SECONDARY_EXEC_DESC to intercept (a subset of)
instructions that are subject to User-Mode Instruction Prevention, i.e.
VMCS.SECONDARY_EXEC_DESC == CR4.UMIP when emulating UMIP.  Preset the
VMCS control when preparing vmcs02 to avoid unnecessarily VMWRITEs,
e.g. KVM will clear VMCS.SECONDARY_EXEC_DESC in prepare_vmcs02_early()
and then set it in vmx_set_cr4().

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 arch/x86/kvm/vmx/nested.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index e4d363661ae7..4b5be38cfc86 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2057,6 +2057,11 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 		/* VMCS shadowing for L2 is emulated for now */
 		exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS;
 
+		/* Preset *DT exiting when emulating UMIP (vmx_set_cr4()). */
+		if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated() &&
+		    (vmcs12->guest_cr4 & X86_CR4_UMIP))
+			exec_control |= SECONDARY_EXEC_DESC;
+
 		if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)
 			vmcs_write16(GUEST_INTR_STATUS,
 				vmcs12->guest_intr_status);
-- 
2.21.0




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