linux-kernel - Re: [PATCH] x86/perf: Fixed kernel panic during boot on Nano processor.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <Y2OS4PgqfavavMKY@zn.tnic>
Date:   Thu, 3 Nov 2022 11:07:28 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     silviazhao-oc <silviazhao-oc@...oxin.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, tglx@...utronix.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        cobechen@...oxin.com, louisqi@...oxin.com, silviazhao@...oxin.com,
        8vvbbqzo567a@...pam.xutrox.com
Subject: Re: [PATCH] x86/perf: Fixed kernel panic during boot on Nano
 processor.

On Thu, Nov 03, 2022 at 11:23:04AM +0800, silviazhao-oc wrote:
> Nano processor may not fully support rdpmc instruction,

What does that even mean? Not fully support?

> it works well for reading general pmc counter, but will lead
> GP(general protection) when accessing fixed pmc counter.

RDPMC will #GP when the perf counter specified cannot be read.

AFAICT, that is RCX: 0000000040000001 which looks like perf counter
index 1 with INTEL_PMC_FIXED_RDPMC_BASE ORed in.

> Furthermore, family/mode information is same between Nano processor
> and ZX-C processor, it leads to zhaoxin pmu driver is wrongly loaded
> for Nano processor, which resulting boot kernal fail.

So *that* is the real problem - it tries to access perf counters
thinking it is running on architectural perf counters implementation but
nano doesn't have that.

> To solve this problem, stepping information will be checked to distinguish
> between Nano processor and ZX-C processor.

Why doesn't that ZXC thing doesn't have a CPUID flag to check instead of
looking at models and steppings and thus confusing it with a nano CPU?

> [https://bugzilla.kernel.org/show_bug.cgi?id=212389]
> 
> Reported-by: Arjan <8vvbbqzo567a@...pam.xutrox.com>

Does Arjan have a last name?

> Signed-off-by: silviazhao-oc <silviazhao-oc@...oxin.com>

I'm assuming your name is properly spelled "Silvia Zhao" and not in a
single word with a "-oc" string appended at the end, yes?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette