On Sat, Jun 28, 2008 at 11:20:47AM +0800, Yang, Sheng wrote: > On Saturday 28 June 2008 02:05:19 Marcelo Tosatti wrote: > > exit_intr_info is read-only in nature, so once read it can be > > cached similarly to idtv_vectoring_inf. > > > > Reduces guest re-entry in about 50 cycles on my machine (the > > exception path should be similar, but haven't measured). > > > > Applies on top of register accessor patch. > > > > Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]> > > > Thanks for the patches! :) > > And I realized there are also too much vmcs_read32 > (CPU_BASED_VM_EXEC_CONTROL)(though not read only). I'd like to post > another patch to optimize it later.
GUEST_INTERRUPTIBILITY_INFO is also a candidate, with significant wins (used by skip_emulated_instruction which is often used in the exit handlers). GUEST_RFLAGS is another register read multiple times in the fast path, but seems trickier. Do you have a better suggestion instead of vmcs_cache_read32/vmcs_cache_write32 below for this caching optimizations? With these three patches applied gettimeofday() microbenchmark is 5% faster. Index: kvm.speed/arch/x86/kvm/vmx.c =================================================================== --- kvm.speed.orig/arch/x86/kvm/vmx.c +++ kvm.speed/arch/x86/kvm/vmx.c @@ -61,6 +61,7 @@ struct vcpu_vmx { u8 fail; u32 idt_vectoring_info; u32 exit_intr_info; + u32 interruptibility; struct kvm_msr_entry *guest_msrs; struct kvm_msr_entry *host_msrs; int nmsrs; @@ -415,6 +416,17 @@ static u64 vmcs_read64(unsigned long fie #endif } +static u32 vmcs_cache_read32(struct kvm_vcpu *vcpu, unsigned long field) +{ + struct vcpu_vmx *vmx = to_vmx(vcpu); + switch(field) { + case GUEST_INTERRUPTIBILITY_INFO: + return vmx->interruptibility; + default: + BUG(); + } +} + static noinline void vmwrite_error(unsigned long field, unsigned long value) { printk(KERN_ERR "vmwrite error: reg %lx value %lx (err %d)\n", @@ -451,6 +463,22 @@ static void vmcs_write64(unsigned long f #endif } +static void vmcs_cache_write32(struct kvm_vcpu *vcpu, unsigned long field, + u32 value) +{ + struct vcpu_vmx *vmx = to_vmx(vcpu); + + vmcs_write32(field, value); + + switch (field) { + case GUEST_INTERRUPTIBILITY_INFO: + vmx->interruptibility = value; + break; + default: + ; + } +} + static void vmcs_clear_bits(unsigned long field, u32 mask) { vmcs_writel(field, vmcs_readl(field) & ~mask); @@ -717,9 +745,9 @@ static void skip_emulated_instruction(st * We emulated an instruction, so temporary interrupt blocking * should be removed, if set. */ - interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO); + interruptibility = vmcs_cache_read32(vcpu, GUEST_INTERRUPTIBILITY_INFO); if (interruptibility & 3) - vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, + vmcs_cache_write32(vcpu, GUEST_INTERRUPTIBILITY_INFO, interruptibility & ~3); vcpu->arch.interrupt_window_open = 1; } @@ -2079,7 +2107,7 @@ static int vmx_vcpu_reset(struct kvm_vcp vmcs_write32(GUEST_IDTR_LIMIT, 0xffff); vmcs_write32(GUEST_ACTIVITY_STATE, 0); - vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, 0); + vmcs_cache_write32(vcpu, GUEST_INTERRUPTIBILITY_INFO, 0); vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0); guest_write_tsc(0); @@ -2169,7 +2197,7 @@ static void do_interrupt_requests(struct vcpu->arch.interrupt_window_open = ((vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) && - (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0); + (vmcs_cache_read32(vcpu, GUEST_INTERRUPTIBILITY_INFO) & 3) == 0); if (vcpu->arch.interrupt_window_open && vcpu->arch.irq_summary && @@ -2788,7 +2816,7 @@ static void enable_nmi_window(struct kvm static int vmx_nmi_enabled(struct kvm_vcpu *vcpu) { - u32 guest_intr = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO); + u32 guest_intr = vmcs_cache_read32(vcpu, GUEST_INTERRUPTIBILITY_INFO); return !(guest_intr & (GUEST_INTR_STATE_NMI | GUEST_INTR_STATE_MOV_SS | GUEST_INTR_STATE_STI)); @@ -2796,7 +2824,7 @@ static int vmx_nmi_enabled(struct kvm_vc static int vmx_irq_enabled(struct kvm_vcpu *vcpu) { - u32 guest_intr = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO); + u32 guest_intr = vmcs_cache_read32(vcpu, GUEST_INTERRUPTIBILITY_INFO); return (!(guest_intr & (GUEST_INTR_STATE_MOV_SS | GUEST_INTR_STATE_STI)) && (vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF)); @@ -2850,8 +2878,8 @@ static void vmx_intr_assist(struct kvm_v */ if ((idtv_info_field & VECTORING_INFO_TYPE_MASK) == INTR_TYPE_NMI_INTR && cpu_has_virtual_nmis()) - vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, - vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & + vmcs_cache_write32(vcpu, GUEST_INTERRUPTIBILITY_INFO, + vmcs_cache_read32(vcpu, GUEST_INTERRUPTIBILITY_INFO) & ~GUEST_INTR_STATE_NMI); vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, idtv_info_field @@ -2873,8 +2901,8 @@ static void vmx_intr_assist(struct kvm_v */ if ((exit_intr_info_field & INTR_INFO_UNBLOCK_NMI) && (exit_intr_info_field & INTR_INFO_VECTOR_MASK) != 8) - vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, - vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) | + vmcs_cache_write32(vcpu, GUEST_INTERRUPTIBILITY_INFO, + vmcs_cache_read32(vcpu, GUEST_INTERRUPTIBILITY_INFO) | GUEST_INTR_STATE_NMI); else if (vcpu->arch.nmi_pending) { if (vmx_nmi_enabled(vcpu)) @@ -3055,8 +3083,9 @@ static void vmx_vcpu_run(struct kvm_vcpu if (vmx->rmode.irq.pending) fixup_rmode_irq(vmx); + vmx->interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO); vcpu->arch.interrupt_window_open = - (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & + (vmx->interruptibility & (GUEST_INTR_STATE_STI | GUEST_INTR_STATE_MOV_SS)) == 0; asm("mov %0, %%ds; mov %0, %%es" : : "r"(__USER_DS)); -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html