From 6ea426fdfde44cf10edac9e8f0c33e8b791242a2 Mon Sep 17 00:00:00 2001
From: Andi Kleen <andi@firstfloor.org>
Date: Fri, 19 Nov 2010 13:16:22 +0100
Subject: [PATCH] MCE: Fix vm86 handling for 32bit mce handler

commit a129a7c84582629741e5fa6f40026efcd7a65bd4 upstream.

When running on 32bit the mce handler could misinterpret
vm86 mode as ring 0. This can affect whether it does recovery
or not; it was possible to panic when recovery was actually
possible.

Fix this by always forcing vm86 to look like ring 3.

[ Backport to 3.0 notes:
Things changed there slightly:
   - move mce_get_rip() up. It fills up m->cs and m->ip values which
     are evaluated in mce_severity(). Therefore move it up right before
     the mce_severity call. This seem to be another bug in 3.0?
   - Place the backport (fix m->cs in V86 case) to where m->cs gets
     filled which is mce_get_rip() in 3.0
]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[PG: commit 8ef8fa7479fff9313387b873413f5ae233a2bd04 in v3.0.44]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 8a6f0afa767e..84b313c1297e 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -453,6 +453,13 @@ static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
 	if (regs && (m->mcgstatus & (MCG_STATUS_RIPV|MCG_STATUS_EIPV))) {
 		m->ip = regs->ip;
 		m->cs = regs->cs;
+		/*
+		 * When in VM86 mode make the cs look like ring 3
+		 * always. This is a lie, but it's better than passing
+		 * the additional vm86 bit around everywhere.
+		 */
+		if (v8086_mode(regs))
+			m->cs |= 3;
 	} else {
 		m->ip = 0;
 		m->cs = 0;
@@ -990,6 +997,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 		 */
 		add_taint(TAINT_MACHINE_CHECK);
 
+		mce_get_rip(&m, regs);
 		severity = mce_severity(&m, tolerant, NULL);
 
 		/*
@@ -1028,7 +1036,6 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 		if (severity == MCE_AO_SEVERITY && mce_usable_address(&m))
 			mce_ring_add(m.addr >> PAGE_SHIFT);
 
-		mce_get_rip(&m, regs);
 		mce_log(&m);
 
 		if (severity > worst) {
-- 
1.8.5.2