KVM: VMX: Move MSR_KERNEL_GS_BASE out of the vmx autoload msr area

Currently MSR_KERNEL_GS_BASE is saved and restored as part of the
guest/host msr reloading.  Since we wish to lazy-restore all the other
msrs, save and reload MSR_KERNEL_GS_BASE explicitly instead of using
the common code.

Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 26 insertions, 13 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 17730175aa08..32512519e1ac 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -99,7 +99,8 @@ struct vcpu_vmx {
         int                   save_nmsrs;
         int                   msr_offset_efer;
 #ifdef CONFIG_X86_64
-        int                   msr_offset_kernel_gs_base;
+        u64                   msr_host_kernel_gs_base;
+        u64                   msr_guest_kernel_gs_base;
 #endif
         struct vmcs          *vmcs;
         struct {
@@ -202,7 +203,7 @@ static void ept_save_pdptrs(struct kvm_vcpu *vcpu);
  */
 static const u32 vmx_msr_index[] = {
 #ifdef CONFIG_X86_64
-        MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR, MSR_KERNEL_GS_BASE,
+        MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR,
 #endif
         MSR_EFER, MSR_K6_STAR,
 };
@@ -674,10 +675,10 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
 #endif
 
 #ifdef CONFIG_X86_64
-        if (is_long_mode(&vmx->vcpu))
-                save_msrs(vmx->host_msrs +
-                          vmx->msr_offset_kernel_gs_base, 1);
-
+        if (is_long_mode(&vmx->vcpu)) {
+                rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
+                wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
+        }
 #endif
         load_msrs(vmx->guest_msrs, vmx->save_nmsrs);
         load_transition_efer(vmx);
@@ -711,6 +712,12 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
         save_msrs(vmx->guest_msrs, vmx->save_nmsrs);
         load_msrs(vmx->host_msrs, vmx->save_nmsrs);
         reload_host_efer(vmx);
+#ifdef CONFIG_X86_64
+        if (is_long_mode(&vmx->vcpu)) {
+                rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
+                wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
+        }
+#endif
 }
 
 static void vmx_load_host_state(struct vcpu_vmx *vmx)
@@ -940,9 +947,6 @@ static void setup_msrs(struct vcpu_vmx *vmx)
                 index = __find_msr_index(vmx, MSR_CSTAR);
                 if (index >= 0)
                         move_msr_up(vmx, index, save_nmsrs++);
-                index = __find_msr_index(vmx, MSR_KERNEL_GS_BASE);
-                if (index >= 0)
-                        move_msr_up(vmx, index, save_nmsrs++);
                 /*
                  * MSR_K6_STAR is only needed on long mode guests, and only
                  * if efer.sce is enabled.
@@ -954,10 +958,6 @@ static void setup_msrs(struct vcpu_vmx *vmx)
 #endif
         vmx->save_nmsrs = save_nmsrs;
 
-#ifdef CONFIG_X86_64
-        vmx->msr_offset_kernel_gs_base =
-                __find_msr_index(vmx, MSR_KERNEL_GS_BASE);
-#endif
         vmx->msr_offset_efer = __find_msr_index(vmx, MSR_EFER);
 
         if (cpu_has_vmx_msr_bitmap()) {
@@ -1015,6 +1015,10 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
         case MSR_GS_BASE:
                 data = vmcs_readl(GUEST_GS_BASE);
                 break;
+        case MSR_KERNEL_GS_BASE:
+                vmx_load_host_state(to_vmx(vcpu));
+                data = to_vmx(vcpu)->msr_guest_kernel_gs_base;
+                break;
         case MSR_EFER:
                 return kvm_get_msr_common(vcpu, msr_index, pdata);
 #endif
@@ -1068,6 +1072,10 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
         case MSR_GS_BASE:
                 vmcs_writel(GUEST_GS_BASE, data);
                 break;
+        case MSR_KERNEL_GS_BASE:
+                vmx_load_host_state(vmx);
+                vmx->msr_guest_kernel_gs_base = data;
+                break;
 #endif
         case MSR_IA32_SYSENTER_CS:
                 vmcs_write32(GUEST_SYSENTER_CS, data);
@@ -1559,6 +1567,11 @@ static void vmx_set_efer(struct kvm_vcpu *vcpu, u64 efer)
         struct vcpu_vmx *vmx = to_vmx(vcpu);
         struct kvm_msr_entry *msr = find_msr_entry(vmx, MSR_EFER);
 
+        /*
+         * Force kernel_gs_base reloading before EFER changes, as control
+         * of this msr depends on is_long_mode().
+         */
+        vmx_load_host_state(to_vmx(vcpu));
         vcpu->arch.shadow_efer = efer;
         if (!msr)
                 return;