From: Robert Richter <rrichter@xxxxxxxxxxx> [ Upstream commit 3724ace582d9f675134985727fd5e9811f23c059 ] The grain in EDAC is defined as "minimum granularity for an error report, in bytes". The following calculation of the grain_bits in edac_mc is wrong: grain_bits = fls_long(e->grain) + 1; Where grain_bits is defined as: grain = 1 << grain_bits Example: grain = 8 # 64 bit (8 bytes) grain_bits = fls_long(8) + 1 grain_bits = 4 + 1 = 5 grain = 1 << grain_bits grain = 1 << 5 = 32 Replace it with the correct calculation: grain_bits = fls_long(e->grain - 1); The example gives now: grain_bits = fls_long(8 - 1) grain_bits = fls_long(7) grain_bits = 3 grain = 1 << 3 = 8 Also, check if the hardware reports a reasonable grain != 0 and fallback with a warning to 1 byte granularity otherwise. [ bp: massage a bit. ] Signed-off-by: Robert Richter <rrichter@xxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: "linux-edac@xxxxxxxxxxxxxxx" <linux-edac@xxxxxxxxxxxxxxx> Cc: James Morse <james.morse@xxxxxxx> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Link: https://lkml.kernel.org/r/20190624150758.6695-2-rrichter@xxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/edac/edac_mc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c index 7d3edd7139328..f59511bd99261 100644 --- a/drivers/edac/edac_mc.c +++ b/drivers/edac/edac_mc.c @@ -1246,9 +1246,13 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, if (p > e->location) *(p - 1) = '\0'; - /* Report the error via the trace interface */ - grain_bits = fls_long(e->grain) + 1; + /* Sanity-check driver-supplied grain value. */ + if (WARN_ON_ONCE(!e->grain)) + e->grain = 1; + + grain_bits = fls_long(e->grain - 1); + /* Report the error via the trace interface */ if (IS_ENABLED(CONFIG_RAS)) trace_mc_event(type, e->msg, e->label, e->error_count, mci->mc_idx, e->top_layer, e->mid_layer, -- 2.20.1
