1 files changed, 14 insertions, 2 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d9dcfa27aa84..0acac81f198b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -472,6 +472,7 @@ struct vcpu_vmx {
                 int           gs_ldt_reload_needed;
                 int           fs_reload_needed;
                 u64           msr_host_bndcfgs;
+                unsigned long vmcs_host_cr4;    /* May not match real cr4 */
         } host_state;
         struct {
                 int vm86_active;
@@ -4267,11 +4268,16 @@ static void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
         u32 low32, high32;
         unsigned long tmpl;
         struct desc_ptr dt;
+        unsigned long cr4;
 
         vmcs_writel(HOST_CR0, read_cr0() & ~X86_CR0_TS);  /* 22.2.3 */
-        vmcs_writel(HOST_CR4, read_cr4());  /* 22.2.3, 22.2.5 */
         vmcs_writel(HOST_CR3, read_cr3());  /* 22.2.3  FIXME: shadow tables */
 
+        /* Save the most likely value for this task's CR4 in the VMCS. */
+        cr4 = read_cr4();
+        vmcs_writel(HOST_CR4, cr4);                     /* 22.2.3, 22.2.5 */
+        vmx->host_state.vmcs_host_cr4 = cr4;
+
         vmcs_write16(HOST_CS_SELECTOR, __KERNEL_CS);  /* 22.2.4 */
 #ifdef CONFIG_X86_64
         /*
@@ -7514,7 +7520,7 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
 static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 {
         struct vcpu_vmx *vmx = to_vmx(vcpu);
-        unsigned long debugctlmsr;
+        unsigned long debugctlmsr, cr4;
 
         /* Record the guest's net vcpu time for enforced NMI injections. */
         if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
@@ -7540,6 +7546,12 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
         if (test_bit(VCPU_REGS_RIP, (unsigned long *)&vcpu->arch.regs_dirty))
                 vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
 
+        cr4 = read_cr4();
+        if (unlikely(cr4 != vmx->host_state.vmcs_host_cr4)) {
+                vmcs_writel(HOST_CR4, cr4);
+                vmx->host_state.vmcs_host_cr4 = cr4;
+        }
+
         /* When single-stepping over STI and MOV SS, we must clear the
          * corresponding interruptibility bits in the guest state. Otherwise
          * vmentry fails as it then expects bit 14 (BS) in pending debug