> From: Avi Kivity [mailto:avi@xxxxxxxxxx] > Sent: Monday, August 29, 2011 3:24 PM > > On 08/29/2011 09:09 AM, Tian, Kevin wrote: > > > > static int handle_apic_access(struct kvm_vcpu *vcpu) > > { > > + unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION); > > + int access_type, offset; > > + > > + access_type = (exit_qualification>> 12)& 0xf; > > + offset = exit_qualification& 0xfff; > > + /* > > + * Sane guest uses MOV instead of string operations to > > + * write EOI, with written value not cared. So make a > > + * short-circuit here by avoiding heavy instruction > > + * emulation. > > + */ > > + if ((access_type == 1)&& (offset == APIC_EOI)) { > > Please replace this 1 with a #define. > updated. -- KVM: APIC: avoid instruction emulation for EOI writes Instruction emulation for EOI writes can be skipped, since sane guest simply uses MOV instead of string operations. This is a nice improvement when guest doesn't support x2apic or hyper-V EOI support. a single VM bandwidth is observed with ~8% bandwidth improvement (7.4Gbps->8Gbps), by saving ~5% cycles from EOI emulation. Signed-off-by: Kevin Tian <kevin.tian@xxxxxxxxx> <Based on earlier work from>: Signed-off-by: Eddie Dong <eddie.dong@xxxxxxxxx> Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 57dcbd4..933187e 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -864,6 +864,15 @@ static int apic_mmio_write(struct kvm_io_device *this, return 0; } +void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu) +{ + struct kvm_lapic *apic = vcpu->arch.apic; + + if (apic) + apic_set_eoi(vcpu->arch.apic); +} +EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi); + void kvm_free_lapic(struct kvm_vcpu *vcpu) { if (!vcpu->arch.apic) diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h index 52c9e6b..8287243 100644 --- a/arch/x86/kvm/lapic.h +++ b/arch/x86/kvm/lapic.h @@ -26,6 +26,7 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu); void kvm_lapic_reset(struct kvm_vcpu *vcpu); u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu); void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8); +void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu); void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value); u64 kvm_lapic_get_base(struct kvm_vcpu *vcpu); void kvm_apic_set_version(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 5e8d411..34c094f 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -4538,8 +4538,25 @@ static int handle_xsetbv(struct kvm_vcpu *vcpu) return 1; } +#define APIC_ACCESS_TYPE_W 1 /* Linear write access during inst execution */ static int handle_apic_access(struct kvm_vcpu *vcpu) { + unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION); + int access_type, offset; + + access_type = (exit_qualification >> 12) & 0xf; + offset = exit_qualification & 0xfff; + /* + * Sane guest uses MOV instead of string operations to + * write EOI, with written value not cared. So make a + * short-circuit here by avoiding heavy instruction + * emulation. + */ + if ((access_type == APIC_ACCESS_TYPE_W) && (offset == APIC_EOI)) { + kvm_lapic_set_eoi(vcpu); + skip_emulated_instruction(vcpu); + return 1; + } return emulate_instruction(vcpu, 0) == EMULATE_DONE; } Thanks Kevin
Attachment:
20110829_kvm_eoi_opt.patch
Description: 20110829_kvm_eoi_opt.patch
