linux-kernel - RE: [Bug report] __arch

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Date:   Thu, 29 Jun 2023 09:10:11 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Borislav Petkov' <bp@...en8.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Richard Weinberger <richard@....at>
CC:     Sebastian Sumpf <Sebastian.Sumpf@...ode-labs.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [Bug report] __arch_hweight32/64 x86

From: Borislav Petkov
> Sent: 27 June 2023 05:26
> 
> On Mon, Jun 26, 2023 at 03:41:27PM -0700, Dave Hansen wrote:
> > I'm not even sure that UML needs GENERIC_HWEIGHT.  From a quick glance,
> > it looks like x86 used to use GENERIC_HWEIGHT, but got arch-specific
> > versions later.  UML just never moved over to the arch-specific versions.
> 
> Thanks - that could very well be the explanation.
> 
> That bug report made me blink a couple of times since I did take extra
> precaution to not clobber regs in arch/x86/lib/hweight.S as this was
> part of the whole pain back then with calling a function from asm where
> gcc doesn't even know we're calling a function, see:

Perhaps the asm called function should use a different global
label than the one in the C file.

Then it wouldn't be as fragile.

	David

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