linux-kernel - [PATCH 1/2] kvm: fix spurious interrupt with irqfd

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Message-ID: <20100113171230.GB19798@redhat.com>
Date:	Wed, 13 Jan 2010 19:12:30 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Davide Libenzi <davidel@...ilserver.org>,
	"Michael S. Tsirkin" <mst@...hat.com>, Avi Kivity <avi@...hat.com>,
	kvm@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] kvm: fix spurious interrupt with irqfd

kvm didn't clear irqfd counter on deassign, as a result we could get a
spurious interrupt when irqfd is assigned back. this leads to poor
performance and, in theory, guest crash.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 virt/kvm/eventfd.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 62e4cd9..a9d3fc6 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -72,12 +72,13 @@ static void
 irqfd_shutdown(struct work_struct *work)
 {
 	struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
+	u64 cnt;
 
 	/*
 	 * Synchronize with the wait-queue and unhook ourselves to prevent
 	 * further events.
 	 */
-	remove_wait_queue(irqfd->wqh, &irqfd->wait);
+	eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
 
 	/*
 	 * We know no new events will be scheduled at this point, so block
-- 
1.6.6.144.g5c3af

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