linux-kernel - Re: [PATCH v3 1/5] x86/paravirt: move some functions and defines to alternative

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Date:   Wed, 25 Oct 2023 15:31:07 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ajay Kaher <akaher@...are.com>,
        Alexey Makhalov <amakhalov@...are.com>,
        VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 1/5] x86/paravirt: move some functions and defines to
 alternative

On 25.10.23 12:34, Borislav Petkov wrote:
> On Thu, Oct 19, 2023 at 11:15:16AM +0200, Juergen Gross wrote:
>> +/* Low-level backend functions usable from alternative code replacements. */
>> +DEFINE_ASM_FUNC(x86_nop, "", .entry.text);
>> +EXPORT_SYMBOL_GPL(x86_nop);
> 
> This is all x86 code so you don't really need the "x86_" prefix - "nop"
> is perfectly fine.

There is

#define nop() asm volatile ("nop")

in arch/x86/include/asm/special_insns.h already.

> 
>> +noinstr void x86_BUG(void)
>> +{
>> +	BUG();
>> +}
>> +EXPORT_SYMBOL_GPL(x86_BUG);
> 
> That export is needed for?
> 
> Paravirt stuff in modules?
> 
> It builds here without it - I guess I need to do an allmodconfig.
> 

It might not be needed now, but are you sure we won't need it in future?


Juergen

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