linux-kernel - [PATCH 3.15 38/42] x86/xen: no need to explicitly register an NMI callback

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Date:	Tue,  5 Aug 2014 11:13:52 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Vrabel <david.vrabel@...rix.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Steven Noonan <steven@...inklabs.net>
Subject: [PATCH 3.15 38/42] x86/xen: no need to explicitly register an NMI callback

3.15-stable review patch.  If anyone has any objections, please let me know.

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

From: David Vrabel <david.vrabel@...rix.com>

commit ea9f9274bf4337ba7cbab241c780487651642d63 upstream.

Remove xen_enable_nmi() to fix a 64-bit guest crash when registering
the NMI callback on Xen 3.1 and earlier.

It's not needed since the NMI callback is set by a set_trap_table
hypercall (in xen_load_idt() or xen_write_idt_entry()).

It's also broken since it only set the current VCPU's callback.

Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Reported-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Tested-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: Steven Noonan <steven@...inklabs.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/xen/setup.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -574,13 +574,7 @@ void xen_enable_syscall(void)
 	}
 #endif /* CONFIG_X86_64 */
 }
-void xen_enable_nmi(void)
-{
-#ifdef CONFIG_X86_64
-	if (register_callback(CALLBACKTYPE_nmi, (char *)nmi))
-		BUG();
-#endif
-}
+
 void __init xen_pvmmu_arch_setup(void)
 {
 	HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments);
@@ -595,7 +589,6 @@ void __init xen_pvmmu_arch_setup(void)
 
 	xen_enable_sysenter();
 	xen_enable_syscall();
-	xen_enable_nmi();
 }
 
 /* This function is not called for HVM domains */


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