[PATCH 2/4] KVM: VMX: Move MSR_KERNEL_GS_BASE out of the vmx autoload msr area

Avi Kivity
2009-09-16T12:45:46Z

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>
---
arch/x86/kvm/vmx.c | 34 +++++++++++++++++++++-------------
1 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d3213ac..547881a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -80,7 +80,8 @@ 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 {
@@ -183,7 +184,7 @@ 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,
};
@@ -649,10 +650,10 @@ 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);
@@ -686,6 +687,12 @@ 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)
@@ -915,9 +922,6 @@ 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.
@@ -929,10 +933,6 @@ 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()) {
@@ -990,6 +990,10 @@ 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
@@ -1043,6 +1047,10 @@ 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);
--
1.6.4.1