linux-kernel - Re: [PATCH net-next 1/2] tools: add missing infrastructure for building ptr

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Date:   Mon, 19 Jul 2021 07:58:00 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     davem@...emloft.net, kuba@...nel.org, jasowang@...hat.com,
        nickhu@...estech.com, green.hu@...il.com, deanbo422@...il.com,
        akpm@...ux-foundation.org, yury.norov@...il.com,
        andriy.shevchenko@...ux.intel.com, ojeda@...nel.org,
        ndesaulniers@...ogle.com, joe@...ches.com,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        Eugenio Pérez <eperezma@...hat.com>
Subject: Re: [PATCH net-next 1/2] tools: add missing infrastructure for
 building ptr_ring.h

On Mon, Jul 19, 2021 at 09:40:39AM +0800, Yunsheng Lin wrote:
> On 2021/7/18 10:09, Michael S. Tsirkin wrote:
> > On Tue, Jul 06, 2021 at 10:04:02AM +0800, Yunsheng Lin wrote:
> >> On 2021/7/6 2:39, Michael S. Tsirkin wrote:
> >>> On Mon, Jul 05, 2021 at 11:57:34AM +0800, Yunsheng Lin wrote:
> 
> [..]
> 
> >>>> diff --git a/tools/include/asm/processor.h b/tools/include/asm/processor.h
> >>>> new file mode 100644
> >>>> index 0000000..3198ad6
> >>>> --- /dev/null
> >>>> +++ b/tools/include/asm/processor.h
> >>>> @@ -0,0 +1,36 @@
> >>>> +/* SPDX-License-Identifier: GPL-2.0 */
> >>>> +
> >>>> +#ifndef __TOOLS_LINUX_ASM_PROCESSOR_H
> >>>> +#define __TOOLS_LINUX_ASM_PROCESSOR_H
> >>>> +
> >>>> +#include <pthread.h>
> >>>> +
> >>>> +#if defined(__i386__) || defined(__x86_64__)
> >>>> +#include "../../arch/x86/include/asm/vdso/processor.h"
> >>>> +#elif defined(__arm__)
> >>>> +#include "../../arch/arm/include/asm/vdso/processor.h"
> >>>> +#elif defined(__aarch64__)
> >>>> +#include "../../arch/arm64/include/asm/vdso/processor.h"
> >>>> +#elif defined(__powerpc__)
> >>>> +#include "../../arch/powerpc/include/vdso/processor.h"
> >>>> +#elif defined(__s390__)
> >>>> +#include "../../arch/s390/include/vdso/processor.h"
> >>>> +#elif defined(__sh__)
> >>>> +#include "../../arch/sh/include/asm/processor.h"
> >>>> +#elif defined(__sparc__)
> >>>> +#include "../../arch/sparc/include/asm/processor.h"
> >>>> +#elif defined(__alpha__)
> >>>> +#include "../../arch/alpha/include/asm/processor.h"
> >>>> +#elif defined(__mips__)
> >>>> +#include "../../arch/mips/include/asm/vdso/processor.h"
> >>>> +#elif defined(__ia64__)
> >>>> +#include "../../arch/ia64/include/asm/processor.h"
> >>>> +#elif defined(__xtensa__)
> >>>> +#include "../../arch/xtensa/include/asm/processor.h"
> >>>> +#elif defined(__nds32__)
> >>>> +#include "../../arch/nds32/include/asm/processor.h"
> >>>> +#else
> >>>> +#define cpu_relax()	sched_yield()
> >>>
> >>> Does this have a chance to work outside of kernel?
> >>
> >> I am not sure I understand what you meant here.
> >> sched_yield() is a pthread API, so it should work in the
> >> user space.
> >> And it allow the rigntest to compile when it is built on
> >> the arch which is not handled as above.
> > 
> > It might compile but is likely too heavy to behave
> > reasonably.
> > 
> > Also, given you did not actually test it I don't
> > think you should add such arch code.
> > Note you broke at least s390 here:
> > ../../arch/s390/include/vdso/processor.h
> > does not actually exist. Where these headers
> > do exit they tend to include lots of code which won't
> > build out of kernel.
> 
> You are right, it should be in:
> ../../arch/s390/include/asm/vdso/processor.h
> 
> > 
> > All this is just for cpu_relax - open coding that seems way easier.
> 
> Sure.
> 
> As Eugenio has posted a patchset to fix the compilation, which does
> not seems to be merged yet and may have some merging conflicts with
> this patchset, so either wait for the Eugenio' patchset to be merged
> before proceeding with this patchset, or explicitly note the dependency
> of Eugenio' patchset when sending the new version of patchset. I am not
> familiar with the merging flow of virtio to say which way is better, any
> suggestion how to proceed with this patchset?
> 
> 1. https://lkml.org/lkml/2021/7/6/1132
> 
> > 
> > 
> >>>
> >>>> +#endif
> >>>
> >>> did you actually test or even test build all these arches?
> >>> Not sure we need to bother with hacks like these.
> >>
> >> Only x86_64 and arm64 arches have been built and tested.
> > 
> > In that case I think you should not add code that you
> > have not even built let alone tested.
> 
> Ok.
> 
> > 
> > 
> >> This is added referring the tools/include/asm/barrier.h.
> >>
> >>>
> >>>
> >>>> +
> > 
> > .


I will merge Eugenio's patchset soon.

-- 
MST