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Date:   Fri, 1 May 2020 08:35:52 -0700
From:   Ira Weiny <ira.weiny@intel.com>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Christian Koenig <christian.koenig@amd.com>,
        Huang Rui <ray.huang@amd.com>,
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        Dave Hansen <dave.hansen@linux.intel.com>,
        dri-devel@lists.freedesktop.org,
        "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Paul Mackerras <paulus@samba.org>,
        "H. Peter Anvin" <hpa@zytor.com>, sparclinux@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Helge Deller <deller@gmx.de>, x86@kernel.org,
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        Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        linux-arm-kernel@lists.infradead.org,
        Chris Zankel <chris@zankel.net>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        linux-parisc@vger.kernel.org, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: sparc-related comment, to Re: [PATCH V1 07/10] arch/kmap: Ensure
 kmap_prot visibility
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 <20200501084446.GG27858@infradead.org>
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On Fri, May 01, 2020 at 01:44:46AM -0700, Christoph Hellwig wrote:
> > --- a/arch/sparc/mm/highmem.c
> > +++ b/arch/sparc/mm/highmem.c
> > @@ -33,6 +33,7 @@
> >  #include <asm/vaddrs.h>
> >  
> >  pgprot_t kmap_prot;
> > +EXPORT_SYMBOL(kmap_prot);
> 
> Btw, I don't see why sparc needs this as a variable, as there is just
> a single assignment to it.

Because sparc uses non-standard defines which I'm not familiar with.

        kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);

SRMMU_ET_PTE and friends are defined in 

arch/sparc/include/asm/pgtsrmmu.h

Since I can't readily test sparc this was easier to put out than let 0-day
crank on the entire series checking if including that header in the common
header chain would be an issue.

> 
> If sparc is sorted out we can always make it a define, and use a define
> for kmap_prot that defaults to PAGE_KERNEL, avoiding a little
> more duplication.

Agreed.  But it seems easier as a follow up (for me with 0-day).  Perhaps
someone from sparc can weigh in on the specifics of those defines and why they
are different from the normal ones?  Or even provide a follow on patch?

Ira