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KVM: nVMX: Preset *DT exiting in vmcs02 when emulating UMIP 

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@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-05-07 12:18:02 -07:00 committed by Paolo Bonzini
parent de0286b788
commit 469debdb8b
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kvm/vmx/nested.c
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@ -2085,6 +2085,14 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
/* VMCS shadowing for L2 is emulated for now */ /* VMCS shadowing for L2 is emulated for now */
exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS; exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS;
/*
* Preset *DT exiting when emulating UMIP, so that vmx_set_cr4()
* will not have to rewrite the controls just for this bit.
*/
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) if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)
vmcs_write16(GUEST_INTR_STATUS, vmcs_write16(GUEST_INTR_STATUS,
vmcs12->guest_intr_status); vmcs12->guest_intr_status);