On Tue, Jul 23, 2019 at 09:06:08PM +0800, luferry@xxxxxxx wrote: > From: luferry <luferry@xxxxxxx> > > x2apic_eanbled() costs about 200 cycles > when guest trigger halt pretty high, pi ops in hotpath > > Signed-off-by: luferry <luferry@xxxxxxx> > --- > arch/x86/kvm/vmx/vmx.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index d98eac371c0a..e17dbf011e47 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -186,6 +186,8 @@ static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush); > static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond); > static DEFINE_MUTEX(vmx_l1d_flush_mutex); > > +static int __read_mostly host_x2apic_enabled; > + > /* Storage for pre module init parameter parsing */ > static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush_param = VMENTER_L1D_FLUSH_AUTO; > > @@ -1204,7 +1206,7 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) > > dest = cpu_physical_id(cpu); > > - if (x2apic_enabled()) > + if (host_x2apic_enabled) Instead of caching x2apic_enabled(), this can be: if (x2apic_supported() && x2apic_mode) which will get compiled out if CONFIG_X86_X2APIC=n. It's quite suprising (to me) that 2apic_enabled() reads the MSR in the first place, but at a glance the other users of x2apic_enabled() do need to query the MSR and/or may be called before x2apic_mode is set. > new.ndst = dest; > else > new.ndst = (dest << 8) & 0xFF00; > @@ -7151,7 +7153,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) > > dest = cpu_physical_id(vcpu->cpu); > > - if (x2apic_enabled()) > + if (host_x2apic_enabled) > new.ndst = dest; > else > new.ndst = (dest << 8) & 0xFF00; > @@ -7221,7 +7223,7 @@ static int pi_pre_block(struct kvm_vcpu *vcpu) > */ > dest = cpu_physical_id(vcpu->pre_pcpu); > > - if (x2apic_enabled()) > + if (host_x2apic_enabled) > new.ndst = dest; > else > new.ndst = (dest << 8) & 0xFF00; > @@ -7804,6 +7806,8 @@ static int __init vmx_init(void) > } > #endif > > + host_x2apic_enabled = x2apic_enabled(); > + > r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx), > __alignof__(struct vcpu_vmx), THIS_MODULE); > if (r) > -- > 2.14.1.40.g8e62ba1 > >
