linux-kernel - [PATCH v5 17/18] kvm: ioapic: Lazy update IOAPIC EOI

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Date:   Thu, 14 Nov 2019 14:15:19 -0600
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com, joro@...tes.org,
        vkuznets@...hat.com, rkagan@...tuozzo.com, graf@...zon.com,
        jschoenh@...zon.de, karahmed@...zon.de, rimasluk@...zon.com,
        jon.grimm@....com,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v5 17/18] kvm: ioapic: Lazy update IOAPIC EOI

In-kernel IOAPIC does not receive EOI with AMD SVM AVIC
since the processor accelerate write to APIC EOI register and
does not trap if the interrupt is edge-triggered.

Workaround this by lazy check for pending APIC EOI at the time when
setting new IOPIC irq, and update IOAPIC EOI if no pending APIC EOI.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/ioapic.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index c57b7bb..6fdd88f 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -48,6 +48,11 @@
 static int ioapic_service(struct kvm_ioapic *vioapic, int irq,
 		bool line_status);
 
+static void kvm_ioapic_update_eoi_one(struct kvm_vcpu *vcpu,
+				      struct kvm_ioapic *ioapic,
+				      int trigger_mode,
+				      int pin);
+
 static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
 					  unsigned long addr,
 					  unsigned long length)
@@ -174,6 +179,31 @@ static bool rtc_irq_check_coalesced(struct kvm_ioapic *ioapic)
 	return false;
 }
 
+static void ioapic_lazy_update_eoi(struct kvm_ioapic *ioapic, int irq)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+	union kvm_ioapic_redirect_entry *entry = &ioapic->redirtbl[irq];
+
+	kvm_for_each_vcpu(i, vcpu, ioapic->kvm) {
+		if (!kvm_apic_match_dest(vcpu, NULL, KVM_APIC_DEST_NOSHORT,
+					 entry->fields.dest_id,
+					 entry->fields.dest_mode) ||
+		    kvm_apic_pending_eoi(vcpu, entry->fields.vector))
+			continue;
+
+		/*
+		 * If no longer has pending EOI in LAPICs, update
+		 * EOI for this vetor.
+		 */
+		rtc_irq_eoi(ioapic, vcpu, entry->fields.vector);
+		kvm_ioapic_update_eoi_one(vcpu, ioapic,
+					  entry->fields.trig_mode,
+					  irq);
+		break;
+	}
+}
+
 static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
 		int irq_level, bool line_status)
 {
@@ -192,6 +222,15 @@ static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
 	}
 
 	/*
+	 * AMD SVM AVIC accelerate EOI write and do not trap,
+	 * in-kernel IOAPIC will not be able to receive the EOI.
+	 * In this case, we do lazy update of the pending EOI when
+	 * trying to set IOAPIC irq.
+	 */
+	if (kvm_apicv_activated(ioapic->kvm))
+		ioapic_lazy_update_eoi(ioapic, irq);
+
+	/*
 	 * Return 0 for coalesced interrupts; for edge-triggered interrupts,
 	 * this only happens if a previous edge has not been delivered due
 	 * do masking.  For level interrupts, the remote_irr field tells
-- 
1.8.3.1