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Date: Fri, 17 May 2024 10:46:29 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@alien8.de>, Tony Luck <tony.luck@intel.com>
CC: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Uros Bizjak <ubizjak@gmail.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Arnd Bergmann <arnd@arndb.de>, Mateusz Guzik <mjguzik@gmail.com>,
        Thomas Renninger <trenn@suse.de>, Greg Kroah-Hartman <gregkh@suse.de>,
        Andi Kleen <ak@linux.intel.com>, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev
Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_v3=5D_x86/cpu=3A_Fix_x86=5Fmatch?=
 =?US-ASCII?Q?=5Fcpu=28=29_to_match_just_X86=5FVENDOR=5FINTEL?=
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On May 17, 2024 10:38:11 AM PDT, Borislav Petkov <bp@alien8=2Ede> wrote:
>On Fri, May 17, 2024 at 10:21:34AM -0700, Tony Luck wrote:
>> diff --git a/arch/x86/kernel/cpu/match=2Ec b/arch/x86/kernel/cpu/match=
=2Ec
>> index 8651643bddae=2E=2E996f96cfce68 100644
>> --- a/arch/x86/kernel/cpu/match=2Ec
>> +++ b/arch/x86/kernel/cpu/match=2Ec
>> @@ -39,7 +39,7 @@ const struct x86_cpu_id *x86_match_cpu(const struct x=
86_cpu_id *match)
>>  	struct cpuinfo_x86 *c =3D &boot_cpu_data;
>> =20
>>  	for (m =3D match;
>> -	     m->vendor | m->family | m->model | m->steppings | m->feature;
>> +	     m->vendor | m->family | m->model | m->steppings | m->feature | m=
->flags;
>
>I think this should not do anything implicit even if it is correct but
>should explicitly check
>
>	if (!(m->flags & X86_CPU_ID_FLAG_VENDOR_VALID))
>		continue;
>
>I don't have a clear idea how exactly yet - I need to play with it=2E
>
>Maybe this stupid flow in the loop should be finally fixed into
>something more readable and sensible=2E=2E=2E
>
>Thx=2E
>

Thought: why don't we add VENDOR and CPUID as synthetic CPU feature flags =
as well? Not saying it necessarily solves this specific problem but it migh=
t make some other code more uniform=2E=20

Obviously on x86-64 CPUID is baseline; VENDOR might not be known, however=
=2E