diff options
| author | Avi Kivity <avi@qumranet.com> | 2007-04-17 15:30:24 +0300 |
|---|---|---|
| committer | Avi Kivity <avi@qumranet.com> | 2007-05-03 10:52:29 +0300 |
| commit | 2345df8c555ecb92c0c36172c07d5ac321a92dc7 (patch) | |
| tree | e61e3a6714d4fd06dbddb3d381494e505fd91ff0 | |
| parent | c9047f533373e934b96d19d6a3d313ca2132fbe5 (diff) | |
KVM: VMX: Reduce unnecessary saving of host msrs
THe automatically switched msrs are never changed on the host (with
the exception of MSR_KERNEL_GS_BASE) and thus there is no need to save
them on every vm entry.
This reduces vmexit latency by ~400 cycles on i386 and by ~900 cycles (10%)
on x86_64.
Signed-off-by: Avi Kivity <avi@qumranet.com>
| -rw-r--r-- | drivers/kvm/vmx.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c index 8c0115b5480..3745e6ccc5b 100644 --- a/drivers/kvm/vmx.c +++ b/drivers/kvm/vmx.c @@ -78,6 +78,10 @@ static const u32 vmx_msr_index[] = { }; #define NR_VMX_MSR ARRAY_SIZE(vmx_msr_index) +#ifdef CONFIG_X86_64 +static unsigned msr_offset_kernel_gs_base; +#endif + static inline int is_page_fault(u32 intr_info) { return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK | @@ -1129,6 +1133,10 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu) vcpu->host_msrs[j].reserved = 0; vcpu->host_msrs[j].data = data; vcpu->guest_msrs[j] = vcpu->host_msrs[j]; +#ifdef CONFIG_X86_64 + if (index == MSR_KERNEL_GS_BASE) + msr_offset_kernel_gs_base = j; +#endif ++vcpu->nmsrs; } @@ -1760,7 +1768,9 @@ again: fx_save(vcpu->host_fx_image); fx_restore(vcpu->guest_fx_image); - save_msrs(vcpu->host_msrs, vcpu->nmsrs); +#ifdef CONFIG_X86_64 + save_msrs(vcpu->host_msrs + msr_offset_kernel_gs_base, 1); +#endif load_msrs(vcpu->guest_msrs, NR_BAD_MSRS); asm ( |