Messages in this thread | | | Date | Fri, 15 Jan 2021 15:46:58 -0700 | From | Mathieu Poirier <> | Subject | Re: [PATCH v1 3/7] perf cs-etm: Calculate per CPU metadata array size |
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On Mon, Jan 11, 2021 at 12:09:12PM +0000, Mike Leach wrote: > Hi Leo, > > I think there is an issue here in that your modification assumes that > all cpus in the system are of the same ETM type. The original routine > allowed for differing ETM types, thus differing cpu ETM field lengths > between ETMv4 / ETMv3, the field size was used after the relevant > magic number for the cpu ETM was read. > > You have replaced two different sizes - with a single calculated size.
I usually go through an entire patchset before looking at the comments people have made. In this case Mike and I are coming to the exact same conclusion.
I will look at Mike's patch on Monday.
> > Moving forwards we are seeing the newer FEAT_ETE protocol drivers > appearing on the list, which will ultimately need a new metadata > structure. > > We have had discussions within ARM regarding the changing of the > format to be more self describing - which should probably be opened > out to the CS mailing list. > > Regards > > Mike > > > On Mon, 11 Jan 2021 at 07:29, Suzuki K Poulose <suzuki.poulose@arm.com> wrote: > > > > On 1/9/21 7:44 AM, Leo Yan wrote: > > > The metadata array can be extended over time and the tool, if using the > > > predefined macro (like CS_ETMV4_PRIV_MAX for ETMv4) as metadata array > > > size to copy data, it can cause compatible issue within different > > > versions of perf tool. > > > > > > E.g. we recorded a data file with an old version tool, afterwards if > > > use the new version perf tool to parse the file, since the metadata > > > array has been extended and the macro CS_ETMV4_PRIV_MAX has been > > > altered, if use it to parse the perf data with old format, this will > > > lead to mismatch. > > > > > > To maintain backward compatibility, this patch calculates per CPU > > > metadata array size on the runtime, the calculation is based on the > > > info stored in the data file so that it's reliable. > > > > > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > > > > Looks good to me. > > > > Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com> > > > > > -- > Mike Leach > Principal Engineer, ARM Ltd. > Manchester Design Centre. UK
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