linux-kernel - Re: [PATCH] x86/hweight: Fix and improve __arch

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Message-ID: <20250310210753.GZZ89UqRTKo2OE4UOl@fat_crate.local>
Date: Mon, 10 Mar 2025 22:07:53 +0100
From: Borislav Petkov <bp@...en8.de>
To: Uros Bizjak <ubizjak@...il.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/hweight: Fix and improve __arch_hweight{32,64}()
 assembly

On Mon, Mar 10, 2025 at 09:54:25PM +0100, Uros Bizjak wrote:
> Ok, so let it be your way and let's just sweep the issue under the carpet.

Can you please read my mails more carefilly? Where did I say we should sweep
the issue under the carpet?

The commit message should be *perfectly* clear what it is fixing. This

"a) Use ASM_CALL_CONSTRAINT to prevent inline asm that includes call
instruction from being scheduled before the frame pointer gets set
up by the containing function, causing objtool to print a "call
without frame pointer save/setup" warning."

says that objool is printing a warning. When I ask, it is not really printing
a warning but it can potentially do so because the compiler is allowed to
schedule things wrongly.

Do you notice the difference?

Dammit, it is very important *why* a commit message is there - it is not
write-only and people look at it. So *again* *please* be precise when
explaining why your patch exists!

All that stuff has been documented at length:

https://kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes

Thanks.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette