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x86: Fix boot failures on older AMD CPU's 

People with old AMD chips are getting hung boots, because commit
bcb80e5387 ("x86, microcode, AMD: Add microcode revision to
/proc/cpuinfo") moved the microcode detection too early into
"early_init_amd()".

At that point we are *so* early in the booth that the exception tables
haven't even been set up yet, so the whole

	rdmsr_safe(MSR_AMD64_PATCH_LEVEL, &c->microcode, &dummy);

doesn't actually work: if the rdmsr does a GP fault (due to non-existant
MSR register on older CPU's), we can't fix it up yet, and the boot fails.

Fix it by simply moving the code to a slightly later point in the boot
(init_amd() instead of early_init_amd()), since the kernel itself
doesn't even really care about the microcode patchlevel at this point
(or really ever: it's made available to user space in /proc/cpuinfo, and
updated if you do a microcode load).

Reported-tested-and-bisected-by:  Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Bob Tracy <rct@gherkin.frus.com>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2011-12-04 11:57:09 -08:00
parent e5fd47bfab
commit 8e8da023f5
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/kernel/cpu/amd.c
View File

@ -442,8 +442,6 @@ static void __cpuinit bsp_init_amd(struct cpuinfo_x86 *c)
static void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
{
u32 dummy;
early_init_amd_mc(c);
/*
@ -473,12 +471,12 @@ static void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_EXTD_APICID);
}
#endif
rdmsr_safe(MSR_AMD64_PATCH_LEVEL, &c->microcode, &dummy);
}
static void __cpuinit init_amd(struct cpuinfo_x86 *c)
{
u32 dummy;
#ifdef CONFIG_SMP
unsigned long long value;
@ -657,6 +655,8 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
checking_wrmsrl(MSR_AMD64_MCx_MASK(4), mask);
}
}
rdmsr_safe(MSR_AMD64_PATCH_LEVEL, &c->microcode, &dummy);
}
#ifdef CONFIG_X86_32