From f77ac507f893fc00c1b9ea0076f3c9e664b0f9ab Mon Sep 17 00:00:00 2001 From: Jesse Larrew Date: Fri, 13 Mar 2015 11:03:39 -0500 Subject: [PATCH] x86/mce: Use safe MSR accesses for AMD quirk Certain MSRs are only relevant to a kernel in host mode, and kvm had chosen not to implement these MSRs at all for guests. If a guest kernel ever tried to access these MSRs, the result was a general protection fault. KVM will be separately patched to return 0 when these MSRs are read, and this patch ensures that MSR accesses are tolerant of exceptions. Signed-off-by: Jesse Larrew [ Drop {} braces around loop ] Signed-off-by: Borislav Petkov Reviewed-by: Joel Schopp Acked-by: Tony Luck Cc: H. Peter Anvin Cc: Thomas Gleixner Cc: linux-edac@vger.kernel.org Link: http://lkml.kernel.org/r/1426262619-5016-1-git-send-email-jesse.larrew@amd.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/mcheck/mce.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index d760931a4546..196a1e34fe39 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -1541,7 +1541,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c) if (c->x86 == 0x15 && (c->x86_model >= 0x10 && c->x86_model <= 0x1f)) { int i; - u64 val, hwcr; + u64 hwcr; bool need_toggle; u32 msrs[] = { 0x00000413, /* MC4_MISC0 */ @@ -1556,15 +1556,9 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c) if (need_toggle) wrmsrl(MSR_K7_HWCR, hwcr | BIT(18)); - for (i = 0; i < ARRAY_SIZE(msrs); i++) { - rdmsrl(msrs[i], val); - - /* CntP bit set? */ - if (val & BIT_64(62)) { - val &= ~BIT_64(62); - wrmsrl(msrs[i], val); - } - } + /* Clear CntP bit safely */ + for (i = 0; i < ARRAY_SIZE(msrs); i++) + msr_clear_bit(msrs[i], 62); /* restore old settings */ if (need_toggle) -- 2.34.1