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Date: Wed, 28 Sep 2016 16:44:32 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
yang.zhang.wz@...il.com, feng.wu@...el.com, rkrcmar@...hat.com
Subject: Re: [PATCH 3/3] KVM: x86: do not scan IRR twice on APICv vmentry
On 28/09/2016 16:00, Michael S. Tsirkin wrote:
> On Tue, Sep 27, 2016 at 11:20:13PM +0200, Paolo Bonzini wrote:
>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
>> index be8b7ad56dd1..85b79b90e3d0 100644
>> --- a/arch/x86/kvm/lapic.c
>> +++ b/arch/x86/kvm/lapic.c
>> @@ -317,7 +317,7 @@ static int find_highest_vector(void *bitmap)
>> vec >= 0; vec -= APIC_VECTORS_PER_REG) {
>> reg = bitmap + REG_POS(vec);
>> if (*reg)
>> - return fls(*reg) - 1 + vec;
>> + return __fls(*reg) + vec;
>> }
>>
>> return -1;
>
> We checked that *reg is != 0 so __fls is safe.
> It's a correct micro-optimization but why stick it in this patch?
Just because I'm using __fls below in __kvm_apic_update_irr.
Paolo
>> @@ -337,25 +337,32 @@ static u8 count_vectors(void *bitmap)
>> return count;
>> }
>>
>> -void __kvm_apic_update_irr(u32 *pir, void *regs)
>> +int __kvm_apic_update_irr(u32 *pir, void *regs)
>> {
>> - u32 i, pir_val;
>> + u32 i, vec;
>> + u32 pir_val, irr_val;
>> + int max_irr = -1;
>>
>> - for (i = 0; i <= 7; i++) {
>> + for (i = vec = 0; i <= 7; i++, vec += 32) {
>> pir_val = READ_ONCE(pir[i]);
>> + irr_val = *((u32 *)(regs + APIC_IRR + i * 0x10));
>> if (pir_val) {
>> - pir_val = xchg(&pir[i], 0);
>> - *((u32 *)(regs + APIC_IRR + i * 0x10)) |= pir_val;
>> + irr_val |= xchg(&pir[i], 0);
>> + *((u32 *)(regs + APIC_IRR + i * 0x10)) = irr_val;
>> }
>> + if (irr_val)
>> + max_irr = __fls(irr_val) + vec;
>> }
>> +
>> + return max_irr;
>> }
>> EXPORT_SYMBOL_GPL(__kvm_apic_update_irr);
>>
>> -void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir)
>> +int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir)
>> {
>> struct kvm_lapic *apic = vcpu->arch.apic;
>>
>> - __kvm_apic_update_irr(pir, apic->regs);
>> + return __kvm_apic_update_irr(pir, apic->regs);
>> }
>> EXPORT_SYMBOL_GPL(kvm_apic_update_irr);
>>
>> @@ -376,7 +383,7 @@ static inline int apic_find_highest_irr(struct kvm_lapic *apic)
>> return -1;
>>
>> if (apic->vcpu->arch.apicv_active)
>> - kvm_x86_ops->sync_pir_to_irr(apic->vcpu);
>> + kvm_x86_ops->sync_pir_to_irr(apic->vcpu, false);
>> result = apic_search_irr(apic);
>> ASSERT(result == -1 || result >= 16);
>>
>> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
>> index f60d01c29d51..fc72828c3782 100644
>> --- a/arch/x86/kvm/lapic.h
>> +++ b/arch/x86/kvm/lapic.h
>> @@ -70,8 +70,8 @@ int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
>> bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
>> int short_hand, unsigned int dest, int dest_mode);
>>
>> -void __kvm_apic_update_irr(u32 *pir, void *regs);
>> -void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
>> +int __kvm_apic_update_irr(u32 *pir, void *regs);
>> +int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
>> int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
>> struct dest_map *dest_map);
>> int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 9b4221471e3d..60e53fa2b554 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -4383,7 +4383,7 @@ static void svm_load_eoi_exitmap(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)
>> return;
>> }
>>
>> -static void svm_sync_pir_to_irr(struct kvm_vcpu *vcpu)
>> +static void svm_sync_pir_to_irr(struct kvm_vcpu *vcpu, bool sync_rvi)
>> {
>> return;
>> }
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 207b9aa32915..1edefab54d01 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -4852,17 +4852,6 @@ static void vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
>> kvm_vcpu_kick(vcpu);
>> }
>>
>> -static void vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
>> -{
>> - struct vcpu_vmx *vmx = to_vmx(vcpu);
>> -
>> - if (!pi_test_on(&vmx->pi_desc) ||
>> - !pi_test_and_clear_on(&vmx->pi_desc))
>> - return;
>> -
>> - kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
>> -}
>> -
>> /*
>> * Set up the vmcs's constant host-state fields, i.e., host-state fields that
>> * will not change in the lifetime of the guest.
>> @@ -8609,6 +8598,20 @@ static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
>> }
>> }
>>
>> +static void vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu, bool sync_rvi)
>> +{
>> + struct vcpu_vmx *vmx = to_vmx(vcpu);
>> + int max_irr;
>> +
>> + if (!pi_test_on(&vmx->pi_desc) ||
>> + !pi_test_and_clear_on(&vmx->pi_desc))
>> + return;
>> +
>> + max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
>> + if (sync_rvi)
>> + vmx_hwapic_irr_update(vcpu, max_irr);
>> +}
>> +
>> static void vmx_load_eoi_exitmap(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)
>> {
>> if (!kvm_vcpu_apicv_active(vcpu))
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 604cfbfc5bee..148e14fdc55d 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -2821,7 +2821,7 @@ static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
>> struct kvm_lapic_state *s)
>> {
>> if (vcpu->arch.apicv_active)
>> - kvm_x86_ops->sync_pir_to_irr(vcpu);
>> + kvm_x86_ops->sync_pir_to_irr(vcpu, false);
>>
>> return kvm_apic_get_state(vcpu, s);
>> }
>> @@ -6448,7 +6448,7 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
>> kvm_scan_ioapic_routes(vcpu, vcpu->arch.ioapic_handled_vectors);
>> else {
>> if (vcpu->arch.apicv_active)
>> - kvm_x86_ops->sync_pir_to_irr(vcpu);
>> + kvm_x86_ops->sync_pir_to_irr(vcpu, false);
>> kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors);
>> }
>> bitmap_or((ulong *)eoi_exit_bitmap, vcpu->arch.ioapic_handled_vectors,
>> @@ -6611,8 +6611,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>> * virtual interrupt delivery.
>> */
>> if (vcpu->arch.apicv_active)
>> - kvm_x86_ops->hwapic_irr_update(vcpu,
>> - kvm_lapic_find_highest_irr(vcpu));
>> + kvm_x86_ops->sync_pir_to_irr(vcpu, true);
>> }
>>
>> if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
>> --
>> 1.8.3.1
>
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