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KVM: VMX: Conditionally reload debug register 6 

Only reload debug register 6 if we're running with the guest's
debug registers.  Saves around 150 cycles from the guest lightweight
exit path.

dr6 contains a couple of bits that are updated on #DB, so intercept
that unconditionally and update those bits then.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity 2009-09-01 16:06:25 +03:00
parent 3d53c27d05
commit e8a48342e9
1 changed files with 9 additions and 5 deletions
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14
arch/x86/kvm/vmx.c
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@ -540,10 +540,12 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu)
eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR);
if (!vcpu->fpu_active)
eb |= 1u << NM_VECTOR;
/*
* Unconditionally intercept #DB so we can maintain dr6 without
* reading it every exit.
*/
eb |= 1u << DB_VECTOR;
if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) {
if (vcpu->guest_debug &
(KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
eb |= 1u << DB_VECTOR;
if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
eb |= 1u << BP_VECTOR;
}
@ -3632,7 +3634,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
*/
vmcs_writel(HOST_CR0, read_cr0());
set_debugreg(vcpu->arch.dr6, 6);
if (vcpu->arch.switch_db_regs)
set_debugreg(vcpu->arch.dr6, 6);
asm(
/* Store host registers */
@ -3734,7 +3737,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
| (1 << VCPU_EXREG_PDPTR));
vcpu->arch.regs_dirty = 0;
get_debugreg(vcpu->arch.dr6, 6);
if (vcpu->arch.switch_db_regs)
get_debugreg(vcpu->arch.dr6, 6);
vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
if (vmx->rmode.irq.pending)