linux-kernel - [080/103] KVM: Fix reboot on Intel hosts

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Date:	Fri, 22 Oct 2010 11:51:54 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org, greg@...ah.com
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	mtosatti@...hat.com, avi@...hat.com
Subject: [080/103] KVM: Fix reboot on Intel hosts

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Marcelo Tosatti <mtosatti@...hat.com>

commit ca242ac9960dc61530e25a2c190e4e13fd5f1ecb upstream.

When we reboot, we disable vmx extensions or otherwise INIT gets blocked.
If a task on another cpu hits a vmx instruction, it will fault if vmx is
disabled.  We trap that to avoid a nasty oops and spin until the reboot
completes.

Problem is, we sleep with interrupts disabled.  This blocks smp_send_stop()
from running, and the reboot process halts.

Fix by enabling interrupts before spinning.

Signed-off-by: Avi Kivity <avi@...hat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 virt/kvm/kvm_main.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1942,10 +1942,12 @@ static int kvm_cpu_hotplug(struct notifi
 
 asmlinkage void kvm_handle_fault_on_reboot(void)
 {
-	if (kvm_rebooting)
+	if (kvm_rebooting) {
 		/* spin while reset goes on */
+		local_irq_enable();
 		while (true)
 			;
+	}
 	/* Fault while not rebooting.  We want the trace. */
 	BUG();
 }


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