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KVM: VMX: Avoid writing HOST_CR0 every entry 

cr0.ts may change between entries, so we copy cr0 to HOST_CR0 before each
entry.  That is slow, so instead, set HOST_CR0 to have TS set unconditionally
(which is a safe value), and issue a clts() just before exiting vcpu context
if the task indeed owns the fpu.

Saves ~50 cycles/exit.

Signed-off-by: Avi Kivity <avi@redhat.com>
hifive-unleashed-5.1
Avi Kivity 2010-05-03 16:05:44 +03:00
parent 08acfa1871
commit 1c11e71357
2 changed files with 4 additions and 7 deletions
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9
arch/x86/kvm/vmx.c
View File

@ -812,6 +812,8 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
}
#endif
if (current_thread_info()->status & TS_USEDFPU)
clts();
}
static void vmx_load_host_state(struct vcpu_vmx *vmx)
@ -2507,7 +2509,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, !!bypass_guest_pf);
vmcs_write32(CR3_TARGET_COUNT, 0); /* 22.2.1 */
vmcs_writel(HOST_CR0, read_cr0()); /* 22.2.3 */
vmcs_writel(HOST_CR0, read_cr0() | X86_CR0_TS); /* 22.2.3 */
vmcs_writel(HOST_CR4, read_cr4()); /* 22.2.3, 22.2.5 */
vmcs_writel(HOST_CR3, read_cr3()); /* 22.2.3 FIXME: shadow tables */
@ -3859,11 +3861,6 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
vmx_set_interrupt_shadow(vcpu, 0);
/*
* Loading guest fpu may have cleared host cr0.ts
*/
vmcs_writel(HOST_CR0, read_cr0());
asm(
/* Store host registers */
"push %%"R"dx; push %%"R"bp;"

2
arch/x86/kvm/x86.c
View File

@ -1731,8 +1731,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
kvm_put_guest_fpu(vcpu);
kvm_x86_ops->vcpu_put(vcpu);
kvm_put_guest_fpu(vcpu);
}
static int is_efer_nx(void)