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Groups > linux.debian.kernel > #71699 > unrolled thread

Bug#979765: rdpmc on VIA Nano

Started by8vvbbqzo567a@nospam.xutrox.com
First post2021-05-18 23:00 +0200
Last post2021-05-20 20:10 +0200
Articles 2 — 1 participant

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  Bug#979765: rdpmc on VIA Nano 8vvbbqzo567a@nospam.xutrox.com - 2021-05-18 23:00 +0200
    Bug#979765: rdpmc on VIA Nano 8vvbbqzo567a@nospam.xutrox.com - 2021-05-20 20:10 +0200

#71699 — Bug#979765: rdpmc on VIA Nano

From8vvbbqzo567a@nospam.xutrox.com
Date2021-05-18 23:00 +0200
SubjectBug#979765: rdpmc on VIA Nano
Message-ID<CgeYO-80q-1@gated-at.bofh.it>
Hello Kazimierz,

The rdpmc instruction can't be used to read the fixed counter on some
VIA Nano CPU's. We're trying to figure out which ones work and which
ones don't work.

Can you provide CPU information from /proc/cpuinfo for your
VIA  Nano U3500 and VIA Eden X2 U4200 CPU's?

Can you also provide the kernel boot messages for your working VIA Eden
X2 U4200? The most interesting part is about the performance events.
Example from my VIA Nano L2200:
[    1.009527] smpboot: CPU0: Centaur VIA Nano processor L2200@1600MHz (family: 0x6, model: 0xf, stepping: 0x2)
[    1.011855] Performance Events:
[    1.011858] core: Welcome to zhaoxin pmu!
[    1.019298] core: Version check pass!
[    1.023297] ZXC events, zhaoxin PMU driver.
[    1.027299] ... version:                2
[    1.031297] ... bit width:              40
[    1.035297] ... generic registers:      3
[    1.039297] ... value mask:             000000ffffffffff
[    1.043297] ... max period:             0000007fffffffff
[    1.047297] ... fixed-purpose events:   3
[    1.051297] ... event mask:             0000000700000007

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#71715

From8vvbbqzo567a@nospam.xutrox.com
Date2021-05-20 20:10 +0200
Message-ID<CgVho-dF-1@gated-at.bofh.it>
In reply to#71699
Thanks for the information.

The U3500 results with the liquorix kernel are unexpected.
I thought that performance events would be completely disabled, but
that's not the case. I'll try to figure out why it doesn't crash.

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