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powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems

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commit fc37a1632d upstream.

PowerVM systems running compatibility mode on a few Power8 revisions are
still vulnerable to the hardware defect that loses PMU exceptions arriving
prior to a context switch.

The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG
cpu_feature bit, nevertheless this bit also needs to be set for PowerVM
compatibility mode systems.

Fixes: 68f2f0d431 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG")
Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com>
Reviewed-by: Leonardo Bras <leonardo@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200227134715.9715-1-desnesn@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Desnes A. Nunes do Rosario 2020-02-27 10:47:15 -03:00 committed by Greg Kroah-Hartman
parent 956b5b1c03
commit d78934442b
1 changed files with 3 additions and 1 deletions
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4
arch/powerpc/kernel/cputable.c
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@ -2232,11 +2232,13 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
* oprofile_cpu_type already has a value, then we are
* possibly overriding a real PVR with a logical one,
* and, in that case, keep the current value for
* oprofile_cpu_type.
* oprofile_cpu_type. Futhermore, let's ensure that the
* fix for the PMAO bug is enabled on compatibility mode.
*/
if (old.oprofile_cpu_type != NULL) {
t->oprofile_cpu_type = old.oprofile_cpu_type;
t->oprofile_type = old.oprofile_type;
t->cpu_features |= old.cpu_features & CPU_FTR_PMAO_BUG;
}
}