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perf/x86: Fix microcode revision check for SNB-PEBS
The following patch makes the microcode update code path actually invoke the perf_check_microcode() function and thus potentially renabling SNB PEBS. By default, CONFIG_MICROCODE_OLD_INTERFACE is forced to Y in arch/x86/Kconfig. There is no way to disable this. That means that the code path used in arch/x86/kernel/microcode_core.c did not include the call to perf_check_microcode(). Thus, even though the microcode was updated to a version that fixes the SNB PEBS problem, perf_event would still return EOPNOTSUPP when enabling precise sampling. This patch simply adds a call to perf_check_microcode() in the call path used when OLD_INTERFACE=y. Signed-off-by: Stephane Eranian <eranian@google.com> Acked-by: Borislav Petkov <borislav.petkov@amd.com> Cc: peterz@infradead.org Cc: andi@firstfloor.org Link: http://lkml.kernel.org/r/20120824133434.GA8014@quad Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -225,6 +225,9 @@ static ssize_t microcode_write(struct file *file, const char __user *buf,
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if (do_microcode_update(buf, len) == 0)
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ret = (ssize_t)len;
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if (ret > 0)
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perf_check_microcode();
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mutex_unlock(µcode_mutex);
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put_online_cpus();
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