[PATCH 1/2] x86, CPU, AMD: Fix WC+ workaround for older hosts
From: Borislav Petkov
The WC+ workaround for F10h introduces a new MSR and kvm host #GPs
on accesses to unknown MSRs if paravirt is not compiled in. Use the
exception-handling MSR accessors so as not to break 3.8 and later guests
booting on older hosts.
Remove a redundant family check while at it.
Cc: Gleb Natapov
Cc: Boris Ostrovsky
Link: http://lkml.kernel.org/r/20130219153655.gd26...@pd.tnic
Signed-off-by: Borislav Petkov
---
arch/x86/kernel/cpu/amd.c | 12 +++-
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 721ef3208eb5..163af4a91d09 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -723,12 +723,14 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
* performance degradation for certain nested-paging guests.
* Prevent this conversion by clearing bit 24 in
* MSR_AMD64_BU_CFG2.
+*
+* NOTE: we want to use the _safe accessors so as not to #GP kvm
+* guests on older kvm hosts.
*/
- if (c->x86 == 0x10) {
- rdmsrl(MSR_AMD64_BU_CFG2, value);
- value &= ~(1ULL << 24);
- wrmsrl(MSR_AMD64_BU_CFG2, value);
- }
+
+ rdmsrl_safe(MSR_AMD64_BU_CFG2, );
+ value &= ~(1ULL << 24);
+ wrmsrl_safe(MSR_AMD64_BU_CFG2, value);
}
rdmsr_safe(MSR_AMD64_PATCH_LEVEL, >microcode, );
--
1.8.1.3.535.ga923c31
--
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[PATCH 1/2] x86, CPU, AMD: Fix WC+ workaround for older hosts
From: Borislav Petkov b...@suse.de
The WC+ workaround for F10h introduces a new MSR and kvm host #GPs
on accesses to unknown MSRs if paravirt is not compiled in. Use the
exception-handling MSR accessors so as not to break 3.8 and later guests
booting on older hosts.
Remove a redundant family check while at it.
Cc: Gleb Natapov g...@redhat.com
Cc: Boris Ostrovsky boris.ostrov...@oracle.com
Link: http://lkml.kernel.org/r/20130219153655.gd26...@pd.tnic
Signed-off-by: Borislav Petkov b...@suse.de
---
arch/x86/kernel/cpu/amd.c | 12 +++-
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 721ef3208eb5..163af4a91d09 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -723,12 +723,14 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
* performance degradation for certain nested-paging guests.
* Prevent this conversion by clearing bit 24 in
* MSR_AMD64_BU_CFG2.
+*
+* NOTE: we want to use the _safe accessors so as not to #GP kvm
+* guests on older kvm hosts.
*/
- if (c-x86 == 0x10) {
- rdmsrl(MSR_AMD64_BU_CFG2, value);
- value = ~(1ULL 24);
- wrmsrl(MSR_AMD64_BU_CFG2, value);
- }
+
+ rdmsrl_safe(MSR_AMD64_BU_CFG2, value);
+ value = ~(1ULL 24);
+ wrmsrl_safe(MSR_AMD64_BU_CFG2, value);
}
rdmsr_safe(MSR_AMD64_PATCH_LEVEL, c-microcode, dummy);
--
1.8.1.3.535.ga923c31
--
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