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>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1773017..3251251 100644 (file)
--- 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;