• Michael Ellerman's avatar
    powerpc/perf: Add an explict flag indicating presence of SLOT field · 7a786832
    Michael Ellerman authored
    In perf_ip_adjust() we potentially use the MMCRA[SLOT] field to adjust
    the reported IP of a sampled instruction.
    
    Currently the logic is written so that if the backend does NOT have
    the PPMU_ALT_SIPR flag set then we assume MMCRA[SLOT] exists.
    
    However on power8 we do not want to set ALT_SIPR (it's in a third
    location), and we also do not have MMCRA[SLOT].
    
    So add a new flag which only indicates whether MMCRA[SLOT] exists.
    
    Naively we'd set it on everything except power6/7, because they set
    ALT_SIPR, and we've reversed the polarity of the flag. But it's more
    complicated than that.
    
    mpc7450 is 32-bit, and uses its own version of perf_ip_adjust()
    which doesn't use MMCRA[SLOT], so it doesn't need the new flag set and
    the behaviour is unchanged.
    
    PPC970 (and I assume power4) don't have MMCRA[SLOT], so shouldn't have
    the new flag set. This is a behaviour change on those cpus, though we
    were probably getting lucky and the bits in question were 0.
    
    power5 and power5+ set the new flag, behaviour unchanged.
    
    power6 & power7 do not set the new flag, behaviour unchanged.
    Signed-off-by: default avatarMichael Ellerman <michael@ellerman.id.au>
    Acked-by: default avatarPaul Mackerras <paulus@samba.org>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    7a786832
power5-pmu.c 16.7 KB