linux-kernel - Re: [tip: x86/urgent] x86/cpu: Provide default cache line size if not enumerated

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Date: Thu, 30 May 2024 08:33:18 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Jörn Heusipp <osmanx@...sipp.de>,
 linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 stable@...r.kernel.org, x86@...nel.org, Thomas Gleixner
 <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Adam Dunlap <acdunlap@...gle.com>
Subject: Re: [tip: x86/urgent] x86/cpu: Provide default cache line size if not
 enumerated

On 5/30/24 08:05, Jörn Heusipp wrote:
>>
>> +        /* Provide a sane default if not enumerated: */
>> +        if (!c->x86_clflush_size)
>> +            c->x86_clflush_size = 32;
>>       } else {
>>           cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
>>
> 
> That honestly looks like a mis-merge to me. This is not what I did test.
> x86_clflush_size needs to get set in the top-level else branch in which
> it is not already set. commit 95bfb35269b2e85cff0dd2c957b2d42ebf95ae5f
> had switched the if branches around.

You're totally right.  Thank you for catching that.

I think a variable removal flipped that code around and it confused me
when I did the rebase.  It should be fixed up now.

Again, thanks a bunch for the report, the testing, and catching my
screwup quickly!