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KVM: VMX: Optimize atomic EFER load 

When NX is enabled on the host but not on the guest, we use the entry/exit
msr load facility, which is slow.  Optimize it to use entry/exit efer load,
which is ~1200 cycles faster.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity 2010-12-21 12:54:20 +02:00
parent 07c116d2f5
commit 110312c84b
1 changed files with 30 additions and 0 deletions
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30
arch/x86/kvm/vmx.c
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@ -191,6 +191,8 @@ static unsigned long *vmx_io_bitmap_b;
static unsigned long *vmx_msr_bitmap_legacy;
static unsigned long *vmx_msr_bitmap_longmode;
static bool cpu_has_load_ia32_efer;
static DECLARE_BITMAP(vmx_vpid_bitmap, VMX_NR_VPIDS);
static DEFINE_SPINLOCK(vmx_vpid_lock);
@ -664,6 +666,12 @@ static void clear_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr)
unsigned i;
struct msr_autoload *m = &vmx->msr_autoload;
if (msr == MSR_EFER && cpu_has_load_ia32_efer) {
vmcs_clear_bits(VM_ENTRY_CONTROLS, VM_ENTRY_LOAD_IA32_EFER);
vmcs_clear_bits(VM_EXIT_CONTROLS, VM_EXIT_LOAD_IA32_EFER);
return;
}
for (i = 0; i < m->nr; ++i)
if (m->guest[i].index == msr)
break;
@ -683,6 +691,14 @@ static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
unsigned i;
struct msr_autoload *m = &vmx->msr_autoload;
if (msr == MSR_EFER && cpu_has_load_ia32_efer) {
vmcs_write64(GUEST_IA32_EFER, guest_val);
vmcs_write64(HOST_IA32_EFER, host_val);
vmcs_set_bits(VM_ENTRY_CONTROLS, VM_ENTRY_LOAD_IA32_EFER);
vmcs_set_bits(VM_EXIT_CONTROLS, VM_EXIT_LOAD_IA32_EFER);
return;
}
for (i = 0; i < m->nr; ++i)
if (m->guest[i].index == msr)
break;
@ -1418,6 +1434,14 @@ static __init int adjust_vmx_controls(u32 ctl_min, u32 ctl_opt,
return 0;
}
static __init bool allow_1_setting(u32 msr, u32 ctl)
{
u32 vmx_msr_low, vmx_msr_high;
rdmsr(msr, vmx_msr_low, vmx_msr_high);
return vmx_msr_high & ctl;
}
static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
{
u32 vmx_msr_low, vmx_msr_high;
@ -1532,6 +1556,12 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
vmcs_conf->vmexit_ctrl = _vmexit_control;
vmcs_conf->vmentry_ctrl = _vmentry_control;
cpu_has_load_ia32_efer =
allow_1_setting(MSR_IA32_VMX_ENTRY_CTLS,
VM_ENTRY_LOAD_IA32_EFER)
&& allow_1_setting(MSR_IA32_VMX_EXIT_CTLS,
VM_EXIT_LOAD_IA32_EFER);
return 0;
}