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

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Message-ID: <20250310213429.GAZ89a5bv2MK_N35mU@fat_crate.local>
Date: Mon, 10 Mar 2025 22:34:29 +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 10:18:50PM +0100, Uros Bizjak wrote:
> a) Use ASM_CALL_CONSTRAINT to prevent inline asm that includes call
> instruction from being scheduled by the compiler before the frame
> pointer gets set
> up by the containing function. This unconstrained scheduling might
> cause objtool to print a "call without frame pointer save/setup"
> warning.
> 
> would be ok?

Yes, and pls say something along the lines of: this is not a currently
triggered issue but it can potentially happen, so that it is perfectly clear
what this patch is addressing.

Thx.

-- 
Regards/Gruss,
    Boris.

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