diff options
| author | Borislav Petkov | 2013-02-19 19:33:12 +0100 |
|---|---|---|
| committer | H. Peter Anvin | 2013-02-19 10:44:00 -0800 |
| commit | 52d3d06e706bdde3d6c5c386deb065c3b4c51618 (patch) | |
| tree | bc9ef29b1ea13a0a7f601379e9041715e9637cd2 /arch/x86 | |
| parent | f0322bd341fd63261527bf84afd3272bcc2e8dd3 (diff) | |
x86, cpu, amd: Fix WC+ workaround for older virtual hosts
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 <gleb@redhat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1361298793-31834-1-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/cpu/amd.c | 12 |
1 files 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); |