Re: [PATCH v2] powerpc: A new cache geometry aux vectors

Paul Clarke [off-list ref] writes:

On 03/02/2017 12:33 AM, Michael Ellerman wrote:

quoted

Paul Clarke [off-list ref] writes:

quoted

On 02/02/2017 12:22 AM, Benjamin Herrenschmidt wrote:

quoted

This adds AUX vectors for the L1I,D, L2 and L3 cache levels
providing for each cache level the size of the cache in bytes
and the geometry (line size and number of ways).

We chose to not use the existing alpha/sh definition which
packs all the information in a single entry per cache level as
it is too restricted to represent some of the geometries used
on POWER.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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v2. Remove some leftovers and fix 32-bit build

Paul, can you test & ack this please ? It replaces the last patch of
my previous series (the rest is identical).

Sorry for the delay on this, I totally missed this e-mail until this week.

I tested this with the Power Functional Simulator (a.k.a. Mambo), with
a fairly recent 4.9 kernel from the powerpc git tree.

You mean 4.9 plus this patch?

quoted

Using Mambo-P8, I see what I expect for cache line size, but associativity is 0:
AT_L1I_CACHESIZE: 32768 (0x8000)
AT_L1I_CACHEGEOMETRY: associativity 0; line size 128
AT_L1D_CACHESIZE: 32768 (0x8000)
AT_L1D_CACHEGEOMETRY: associativity 0; line size 128
AT_L2_CACHESIZE: 524288 (0x80000)
AT_L2_CACHEGEOMETRY: associativity 0; line size 128
AT_L3_CACHESIZE: 8388608 (0x800000)
AT_L3_CACHEGEOMETRY: associativity 0; line size 128

...shouldn't associativity be 8 for all levels?

Yes.

I fixed it in v3: http://patchwork.ozlabs.org/patch/723576/

Which is now merged in Linus tree, so please test that.

It's not working for me, but it's also very likely that I could be
doing something stupid. Just pulling from
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git, it
built (without the "systemsim" patches"), but wouldn't boot in Mambo
(not because it couldn't find root...something else not fully
explored).

Hmm OK, it's booting for me, but might depend on your config/toolchain
etc. Linus' tree just before rc1 is a bit of a dangerous place to be.

I checked out tag "v4.10", and that built (with the
"systemsim" patches, Ben's 1-8 and your 9v3) and booted.

I think you need my entire v3, ignore Ben's series.

On Mambo-P8,
the device tree looks correct (to me), but the associativity is still
0.

OK, I think if you use the full v3 the associativity will be fixed.

Though it might still be wrong, because the kernel code hard codes the
values on P8 bare metal, because on real machines (running skiboot) the
values provided in the device tree are wrong.

Hopefully those hard coded values are also correct on p8 mambo, but we
should probably check.

See: https://git.kernel.org/torvalds/c/608b42140e96

On P9, the device tree isn't correct, so I'm not sure what to expect.

Junk :)

On P9 it all comes from the device tree so if that's wrong the AUX
vectors will definitely be wrong.

quoted

Can you try the test program I wrote (which may also have bugs):

  http://patchwork.ozlabs.org/patch/724418/

I couldn't get this working, either, so I'm probably doing something stupid.

Did you apply the first patch of the series also?

If you apply those on top of v4.10 and then do:

$ make TARGETS=powerpc ARCH=powerpc CROSS_COMPILE=ppc64le- -C tools/testing/selftests

You should end up with:

$ file tools/testing/selftests/powerpc/cache_shape/cache_shape
tools/testing/selftests/powerpc/cache_shape/cache_shape: ELF 64-bit LSB executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked, interpreter /lib64/ld64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=3535b7ab6ec854eceaa7ad23456a087111b51583, not stripped


cheers