linux-kernel - [PATCH] KVM: x86: don't notify userspace IOAPIC on edge EOI

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Message-Id: <1444329000-8723-1-git-send-email-rkrcmar@redhat.com>
Date:	Thu,  8 Oct 2015 20:30:00 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
	Steve Rutherford <srutherford@...gle.com>
Subject: [PATCH] KVM: x86: don't notify userspace IOAPIC on edge EOI

On real hardware, edge-triggered interrupts don't set a bit in TMR,
which means that IOAPIC isn't notified on EOI.  Do the same here.

Staying in guest/kernel mode after edge EOI is what we want for most
devices.  If some bugs could be nicely worked around with edge EOI
notifications, we should invest in a better interface.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 Completely untested.
 
 arch/x86/kvm/irq_comm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index c89228980230..8f4499c7ffc1 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -389,13 +389,15 @@ void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)
 	for (i = 0; i < nr_ioapic_pins; ++i) {
 		hlist_for_each_entry(entry, &table->map[i], link) {
 			u32 dest_id, dest_mode;
+			bool level;
 
 			if (entry->type != KVM_IRQ_ROUTING_MSI)
 				continue;
 			dest_id = (entry->msi.address_lo >> 12) & 0xff;
 			dest_mode = (entry->msi.address_lo >> 2) & 0x1;
-			if (kvm_apic_match_dest(vcpu, NULL, 0, dest_id,
-						dest_mode)) {
+			level = entry->msi.data & MSI_DATA_TRIGGER_LEVEL;
+			if (level && kvm_apic_match_dest(vcpu, NULL, 0,
+						dest_id, dest_mode)) {
 				u32 vector = entry->msi.data & 0xff;
 
 				__set_bit(vector,
-- 
2.5.3

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