linux-kernel - Re: [PATCH] x86/cacheinfo: fix a -Wtype-limits warning

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Message-ID: <20190619170127.GF9574@zn.tnic>
Date:   Wed, 19 Jun 2019 19:01:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Qian Cai <cai@....pw>, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/cacheinfo: fix a -Wtype-limits warning

On Wed, Jun 05, 2019 at 01:07:04PM -0700, Sean Christopherson wrote:
> Might be worth calling out in the changelog that 'c->x86 == 0x17' is true
> if and only if c->x86_model was explicitly set by cpu_detect(), i.e. the
> patch is correct even if the original intent was a misguided attempt to
> check that x86_model has been set.

Are you thinking about some sick virt scenario where base CPUID level is < 1?

In this particular case, there's a guard at the beginning of
cacheinfo_amd_init_llc_id():

        if (!cpuid_edx(0x80000006))
                return;

but if there's CPUs which have CPUID 0x80000006 but base CPUID level is
< 1, then that's their problem.

-- 
Regards/Gruss,
    Boris.

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