linux-kernel - Re: [PATCH 08/19] mm: Always define pxx

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Message-ID: <ZrzQjEJG3rEZhLTE@x1n>
Date: Wed, 14 Aug 2024 11:43:08 -0400
From: Peter Xu <peterx@...hat.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Sean Christopherson <seanjc@...gle.com>,
	Oscar Salvador <osalvador@...e.de>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
	Will Deacon <will@...nel.org>, Gavin Shan <gshan@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>, Zi Yan <ziy@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Alistair Popple <apopple@...dia.com>,
	Borislav Petkov <bp@...en8.de>,
	David Hildenbrand <david@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, kvm@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Yan Zhao <yan.y.zhao@...el.com>
Subject: Re: [PATCH 08/19] mm: Always define pxx_pgprot()

On Wed, Aug 14, 2024 at 10:09:15AM -0300, Jason Gunthorpe wrote:
> On Fri, Aug 09, 2024 at 12:08:58PM -0400, Peter Xu wrote:
> > There're:
> > 
> >   - 8 archs (arc, arm64, include, mips, powerpc, s390, sh, x86) that
> >   support pte_pgprot().
> > 
> >   - 2 archs (x86, sparc) that support pmd_pgprot().
> > 
> >   - 1 arch (x86) that support pud_pgprot().
> > 
> > Always define them to be used in generic code, and then we don't need to
> > fiddle with "#ifdef"s when doing so.
> > 
> > Signed-off-by: Peter Xu <peterx@...hat.com>
> > ---
> >  arch/arm64/include/asm/pgtable.h    |  1 +
> >  arch/powerpc/include/asm/pgtable.h  |  1 +
> >  arch/s390/include/asm/pgtable.h     |  1 +
> >  arch/sparc/include/asm/pgtable_64.h |  1 +
> >  include/linux/pgtable.h             | 12 ++++++++++++
> >  5 files changed, 16 insertions(+)
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> 
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index 7a4f5604be3f..b78cc4a6758b 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -384,6 +384,7 @@ static inline void __sync_cache_and_tags(pte_t pte, unsigned int nr_pages)
> >  /*
> >   * Select all bits except the pfn
> >   */
> > +#define pte_pgprot pte_pgprot
> >  static inline pgprot_t pte_pgprot(pte_t pte)
> >  {
> >  	unsigned long pfn = pte_pfn(pte);
> 
> Stylistically I've been putting the #defines after the function body,
> I wonder if there is a common pattern..

Right, I see both happening in tree right now and I don't know which is
better.  Personally I preferred "before function" as it makes spell checks
easy to match macro/func names, and also cscope indexes both macro and
func, so a jump to any of them would make me look at the entry of func.

I'll keep it as-is for now just to make it easy for me.. but please comment
if we do have a preferred pattern the other way round, then I'll follow.

Thanks,

-- 
Peter Xu