linux-kernel - Re: [PATCH] [v2] x86: xen: add missing prototypes

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Date:   Tue, 23 May 2023 22:37:09 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
        "Arnd Bergmann" <arnd@...nel.org>,
        "Juergen Gross" <jgross@...e.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "Stefano Stabellini" <sstabellini@...nel.org>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        "Oleksandr Tyshchenko" <oleksandr_tyshchenko@...m.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] x86: xen: add missing prototypes

On Sat, May 20, 2023, at 00:24, Boris Ostrovsky wrote:
> On 5/19/23 5:28 AM, Arnd Bergmann wrote:
>
>> diff --git a/arch/x86/xen/smp.h b/arch/x86/xen/smp.h
>> index 22fb982ff971..81a7821dd07f 100644
>> --- a/arch/x86/xen/smp.h
>> +++ b/arch/x86/xen/smp.h
>> @@ -1,7 +1,11 @@
>>   /* SPDX-License-Identifier: GPL-2.0 */
>>   #ifndef _XEN_SMP_H
>>   
>> +void asm_cpu_bringup_and_idle(void);
>> +asmlinkage void cpu_bringup_and_idle(void);
>
> These can go under CONFIG_SMP

Not sure if there is much point for the second one, since
it's only called from assembler, so the #else path is
never seen, but I can do that for consistency if you
like.

I generally prefer to avoid the extra #if checks
when there is no strict need for an empty stub.

I guess you also want me to add the empty stubs for the
other functions that only have a bit in #ifdef but not
#else then?

>> +void xen_force_evtchn_callback(void);
>
> These ...
>
>> +pteval_t xen_pte_val(pte_t pte);
>> +pgdval_t xen_pgd_val(pgd_t pgd);
>> +pte_t xen_make_pte(pteval_t pte);
>> +pgd_t xen_make_pgd(pgdval_t pgd);
>> +pmdval_t xen_pmd_val(pmd_t pmd);
>> +pmd_t xen_make_pmd(pmdval_t pmd);
>> +pudval_t xen_pud_val(pud_t pud);
>> +pud_t xen_make_pud(pudval_t pud);
>> +p4dval_t xen_p4d_val(p4d_t p4d);
>> +p4d_t xen_make_p4d(p4dval_t p4d);
>> +pte_t xen_make_pte_init(pteval_t pte);
>> +void xen_start_kernel(struct start_info *si);
>
>
> ... should go under '#ifdef CONFIG_XEN_PV'

What should the stubs do here? I guess just return the
unmodified value?

    Arnd