linux-kernel - Re: [PATCH 2/5] KVM: x86: do not scan IRR twice on APICv vmentry

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Date:   Thu, 3 Nov 2016 16:03:57 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        yang.zhang.wz@...il.com, feng.wu@...el.com, mst@...hat.com
Subject: Re: [PATCH 2/5] KVM: x86: do not scan IRR twice on APICv vmentry

2016-11-03 14:30+0100, Paolo Bonzini:
> On 26/10/2016 21:59, Radim Krčmář wrote:
>> 2016-10-14 20:21+0200, Paolo Bonzini:
>>> Calling apic_find_highest_irr results in IRR being scanned twice,
>>> once in vmx_sync_pir_from_irr and once in apic_search_irr.  Change
>>> sync_pir_from_irr to do the RVI write and kvm_apic_update_irr to
>>> compute the new RVI on the fly.
>>>
>>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>>> ---
>> 
>> Reviewed-by: Radim Krčmář <rkrcmar@...hat.com>
> 
> Nope, this breaks nested VMX exit on external interrupt.  For now I'm
> testing only patch 1 and will push that one only to kvm/next.

Hm, does it also happen with this change?

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4b20f7304b9c..6be110e53e9e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -941,7 +941,7 @@ struct kvm_x86_ops {
 	void (*set_virtual_x2apic_mode)(struct kvm_vcpu *vcpu, bool set);
 	void (*set_apic_access_page_addr)(struct kvm_vcpu *vcpu, hpa_t hpa);
 	void (*deliver_posted_interrupt)(struct kvm_vcpu *vcpu, int vector);
-	void (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
+	int (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
 	int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
 	int (*get_tdp_level)(void);
 	u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index f8157a36ab09..ffa541d38343 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4383,9 +4383,9 @@ 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 int svm_sync_pir_to_irr(struct kvm_vcpu *vcpu)
 {
-	return;
+	return -1; // XXX
 }
 
 static void svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f272ccfddc48..2211e1774733 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8493,17 +8493,15 @@ static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
 	}
 }
 
-static void vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
+static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	int max_irr;
 
 	if (!pi_test_on(&vmx->pi_desc))
 		return;
 
 	pi_clear_on(&vmx->pi_desc);
-	max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
-	vmx_hwapic_irr_update(vcpu, max_irr);
+	return kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
 }
 
 static void vmx_apicv_post_state_restore(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 20d572c18293..e8789f3a9bfd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6675,7 +6675,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		 * notified with kvm_vcpu_kick.
 		 */
 		if (vcpu->arch.apicv_active)
-			kvm_x86_ops->sync_pir_to_irr(vcpu);
+			kvm_x86_ops->hwapic_irr_update(vcpu, kvm_x86_ops->sync_pir_to_irr(vcpu));
 	}
 
 	if (vcpu->mode == EXITING_GUEST_MODE || vcpu->requests