linux-kernel - Re: [PATCH] Handle Ice Lake MONITOR erratum

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Message-ID: <4ea35cc4-1720-494c-9d90-e4669c8cde08@intel.com>
Date: Tue, 22 Apr 2025 07:18:41 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Ingo Molnar <mingo@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, andrew.cooper3@...rix.com,
 Len Brown <len.brown@...el.com>, Peter Zijlstra <peterz@...radead.org>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 stable@...r.kernel.org
Subject: Re: [PATCH] Handle Ice Lake MONITOR erratum

On 4/21/25 23:46, Ingo Molnar wrote:
>>  /*
>> + * These CPUs have buggy MWAIT/MONITOR implementations that
>> + * usually manifest as hangs or stalls at boot.
>> + */
>> +#define MWAIT_VFM(_vfm)	\
>> +	X86_MATCH_VFM_FEATURE(_vfm, X86_FEATURE_MWAIT, 0)
>> +static const struct x86_cpu_id monitor_bug_list[] = {
>> +	MWAIT_VFM(INTEL_ATOM_GOLDMONT),
>> +	MWAIT_VFM(INTEL_LUNARLAKE_M),
>> +	MWAIT_VFM(INTEL_ICELAKE_X),	/* Erratum ICX143 */
>> +	{},
>> +};
> While it's just an internal helper, macro names should still be 
> intuitive:
> 
>   s/MWAIT_VFM
>    /VFM_MWAIT_BUG

The current convention is to end with the thing that's being matched,
like "_FEATURE" or "_VFM" in the X86_MATCH*() macros. That's why I
ordered it the way I did.

As for including "BUG", the _macro_ doesn't match CPUs with the bug.
It's just matching CPUs with the specified VFM that have MWAIT. It could
(theoretically) get used for non-bug things so I don't think it's
intuitive to put "BUG" in the name.

But, honestly, we have a tone of these one-off x86_cpu_id macros around.
They have lots of pretty silly naming, but they're mostly only used at
one isolated site so I don't worry about the naming _too_ much.