x86: Fix boot failures on older AMD CPU's

People with old AMD chips are getting hung boots, because commit
bcb80e53877c ("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 <[email protected]>
Tested-by: Bob Tracy <[email protected]>
Acked-by: Borislav Petkov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Srivatsa S. Bhat <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions