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Commit 110312c8 authored by Avi Kivity's avatar Avi Kivity
Browse files

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: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 07c116d2

arch/x86/kvm/vmx.c

+30 −0
Original line number Diff line number Diff line
@@ -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;

}