KVM: VMX: set vmx->emulation_required only when needed.

If emulate_invalid_guest_state=false vmx->emulation_required is never
actually used, but it ends up to be always set to true since
handle_invalid_guest_state(), the only place it is reset back to
false, is never called. This, besides been not very clean, makes vmexit
and vmentry path to check emulate_invalid_guest_state needlessly.

The patch fixes that by keeping emulation_required coherent with
emulate_invalid_guest_state setting.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9bc68c7bca7d..02eeba86328d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2759,6 +2759,11 @@ static __exit void hardware_unsetup(void)
         free_kvm_area();
 }
 
+static bool emulation_required(struct kvm_vcpu *vcpu)
+{
+        return emulate_invalid_guest_state && !guest_state_valid(vcpu);
+}
+
 static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg,
                 struct kvm_segment *save)
 {
@@ -2794,7 +2799,6 @@ static void enter_pmode(struct kvm_vcpu *vcpu)
         vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_SS], VCPU_SREG_SS);
         vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_CS], VCPU_SREG_CS);
 
-        vmx->emulation_required = 1;
         vmx->rmode.vm86_active = 0;
 
         vmx_segment_cache_clear(vmx);
@@ -2885,7 +2889,6 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
         vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_SS], VCPU_SREG_SS);
         vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_CS], VCPU_SREG_CS);
 
-        vmx->emulation_required = 1;
         vmx->rmode.vm86_active = 1;
 
         /*
@@ -3111,6 +3114,9 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
         vmcs_writel(CR0_READ_SHADOW, cr0);
         vmcs_writel(GUEST_CR0, hw_cr0);
         vcpu->arch.cr0 = cr0;
+
+        /* depends on vcpu->arch.cr0 to be set to a new value */
+        vmx->emulation_required = emulation_required(vcpu);
 }
 
 static u64 construct_eptp(unsigned long root_hpa)
@@ -3298,8 +3304,7 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
         vmcs_write32(sf->ar_bytes, vmx_segment_access_rights(var));
 
 out:
-        if (!vmx->emulation_required)
-                vmx->emulation_required = !guest_state_valid(vcpu);
+        vmx->emulation_required |= emulation_required(vcpu);
 }
 
 static void vmx_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l)
@@ -5027,7 +5032,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
                         schedule();
         }
 
-        vmx->emulation_required = !guest_state_valid(vcpu);
+        vmx->emulation_required = emulation_required(vcpu);
 out:
         return ret;
 }
@@ -5970,7 +5975,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
         u32 vectoring_info = vmx->idt_vectoring_info;
 
         /* If guest state is invalid, start emulating */
-        if (vmx->emulation_required && emulate_invalid_guest_state)
+        if (vmx->emulation_required)
                 return handle_invalid_guest_state(vcpu);
 
         /*
@@ -6253,7 +6258,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 
         /* Don't enter VMX if guest state is invalid, let the exit handler
            start emulation until we arrive back to a valid state */
-        if (vmx->emulation_required && emulate_invalid_guest_state)
+        if (vmx->emulation_required)
                 return;
 
         if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty))