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Subject[17/85] x86, amd: Use _safe() msr access for GartTlbWlk disable code
2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------
From: "Roedel, Joerg" <Joerg.Roedel@amd.com>

commit d47cc0db8fd6011de2248df505fc34990b7451bf upstream.

The workaround for Bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=33012

introduced a read and a write to the MC4 mask msr.

Unfortunatly this MSR is not emulated by the KVM hypervisor
so that the kernel will get a #GP and crashes when applying
this workaround when running inside KVM.

This issue was reported as:

https://bugzilla.kernel.org/show_bug.cgi?id=35132

and is fixed with this patch. The change just let the kernel
ignore any #GP it gets while accessing this MSR by using the
_safe msr access methods.

Reported-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/kernel/cpu/amd.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -585,10 +585,13 @@ static void __cpuinit init_amd(struct cp
* Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=33012
*/
u64 mask;
+ int err;

- rdmsrl(MSR_AMD64_MCx_MASK(4), mask);
- mask |= (1 << 10);
- wrmsrl(MSR_AMD64_MCx_MASK(4), mask);
+ err = rdmsrl_safe(MSR_AMD64_MCx_MASK(4), &mask);
+ if (err == 0) {
+ mask |= (1 << 10);
+ checking_wrmsrl(MSR_AMD64_MCx_MASK(4), mask);
+ }
}
}


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