linux-kernel - Re: [PATCH v4 01/17] x86/common: Align cpu_caps_cleared and cpu_caps

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Message-ID: <20190304101736.GC32477@hirez.programming.kicks-ass.net>
Date:   Mon, 4 Mar 2019 11:17:36 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, kvm@...r.kernel.org
Subject: Re: [PATCH v4 01/17] x86/common: Align cpu_caps_cleared and
 cpu_caps_set to unsigned long

On Mon, Mar 04, 2019 at 09:33:16AM +0100, Paolo Bonzini wrote:
> Why not instead change set_bit/clear_bit to use btsl/btrl instead of
> btsq/btrq?

At least one of the faulty users (wireless) is in generic code and needs
fixing regardless.

For better or worse; the bitmap stuff is defined to work on unsigned
long. Using it on smaller types already relies on small endian; but
further enabling just makes it worse I feel. Better have the rules be
uniform.