linux-kernel - Re: [RFC 01/10] x86/microcode/intel: expose collect_cpu_info

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Date:   Wed, 2 Mar 2022 17:34:10 -0800
From:   "Joseph, Jithu" <jithu.joseph@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <hdegoede@...hat.com>, <markgross@...nel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>,
        <dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
        <corbet@....net>, <gregkh@...uxfoundation.org>,
        <andriy.shevchenko@...ux.intel.com>, <ashok.raj@...el.com>,
        <tony.luck@...el.com>, <rostedt@...dmis.org>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <patches@...ts.linux.dev>,
        <ravi.v.shankar@...el.com>
Subject: Re: [RFC 01/10] x86/microcode/intel: expose collect_cpu_info_early()
 for IFS



On 3/2/2022 2:30 AM, Borislav Petkov wrote:
> On Tue, Mar 01, 2022 at 11:54:48AM -0800, Jithu Joseph wrote:
>> @@ -58,6 +58,7 @@ static inline bool cpu_signatures_match(unsigned int s1, unsigned int p1,
>>  	/* ... or they intersect. */
>>  	return p1 & p2;
>>  }
>> +EXPORT_SYMBOL_GPL(cpu_signatures_match);
...
> 
> Hell, even your function signatures don't match.
> 
> And then, with that fixed it would build but then one would wonder a
> long time why that ifs thing doesn't work. Well:
> 
> # CONFIG_MICROCODE is not set

Thanks for reviewing the patch and pointing out the mistakes of not setting the module build dependency(on CONFIG_MICROCODE) and that of signature mismatch

> 
> So the proper thing to do is to extract the generic functionality for
> comparing microcode patch signatures and for gathering the information
> collect_cpu_info_early() collects, into intel-generic functions, like
> I've done with intel_get_microcode_revision(), move that functionality
> to arch/x86/kernel/cpu/intel.c and then use it *both* in the microcode
> loader *and* your driver.
> 

Will move these two function definitions from arch/x86/kernel/cpu/microcode/intel.c to arch/x86/kernel/cpu/intel.c in the next revision as you suggest above.
Need to find an appropriate header for these moved functions too.


Jithu