linux-kernel - [PATCH 9/9] lguest: don't crash host on NMI

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Date:	Fri, 09 Mar 2007 14:32:56 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andrew Morton <akpm@...l.org>
Cc:	Andi Kleen <ak@....de>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 9/9] lguest: don't crash host on NMI

"handle" NMI by ignoring it.  Can't have been important, right?  As the
lguest64 hackers explained, handling NMI is a PITA.  Now oprofile does
not crash machine.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff -r 5beeb29ed3a3 arch/i386/lguest/hypervisor.S
--- a/arch/i386/lguest/hypervisor.S	Wed Feb 28 09:59:23 2007 +1100
+++ b/arch/i386/lguest/hypervisor.S	Wed Feb 28 09:59:47 2007 +1100
@@ -116,6 +116,11 @@ deliver_to_host:
 	orl	%eax, %edx
 	jmp	*%edx
 
+/* We ignore NMI and return. */
+handle_nmi:
+	addl	$8, %esp
+	iret
+
 /* Real hardware interrupts are delivered straight to the host.  Others
    cause us to return to run_guest_once so it can decide what to do.  Note
    that some of these are overridden by the guest to deliver directly, and
@@ -148,8 +153,7 @@ default_idt_entries:
 default_idt_entries:
 .text
 	IRQ_STUBS 0 1 return_to_host		/* First two traps */
-/* FIXME: NMI needs something completely different.  Don't SWITCH_TO_HOST. */
-	IRQ_STUB 2 deliver_to_host		/* NMI */
+	IRQ_STUB 2 handle_nmi			/* NMI */
 	IRQ_STUBS 3 31 return_to_host		/* Rest of traps */
 	IRQ_STUBS 32 127 deliver_to_host	/* Real interrupts */
 	IRQ_STUB 128 return_to_host		/* System call (overridden) */


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