linux-kernel - [PATCH] KVM: Avoid calling smp_call_function

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Message-Id: <11875282461120-git-send-email-avi@qumranet.com>
Date:	Sun, 19 Aug 2007 15:57:26 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	ornati@...twebnet.it, kvm-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, Avi Kivity <avi@...ranet.com>
Subject: [PATCH] KVM: Avoid calling smp_call_function_single() with interrupts disabled

When taking a cpu down, we need to hardware_disable() it.  Unfortunately,
the CPU_DYING notifier is called with interrupts disabled, which means
we can't use smp_call_function_single().  Fortunately, the CPU_DYING notifier
is always called on the dying cpu, so we don't need to use the function at
all and can simply call hardware_disable() directly.

Tested-by: Paolo Ornati <ornati@...twebnet.it>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---

Linus, please apply to -rc.

 drivers/kvm/kvm_main.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 9685609..cd05579 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -2974,6 +2974,10 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
 	switch (val) {
 	case CPU_DYING:
 	case CPU_DYING_FROZEN:
+		printk(KERN_INFO "kvm: disabling virtualization on CPU%d\n",
+		       cpu);
+		hardware_disable(NULL);
+		break;
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
 		printk(KERN_INFO "kvm: disabling virtualization on CPU%d\n",
-- 
1.5.2.4

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