Re: [PATCH] aio: fix D-cache aliasing issues

[John David Anglin]

On 17-Nov-13, at 7:52 PM, James Bottomley wrote:

> > +void flush_user_dcache_page(struct page *page);
> > +
>
> The split into flush_kernel.. and flush_user.. is pointless.  We  
> have no
> use for a flush_user_.. API because it's not part of the standard  
> linux
> one.  Plus it's going to confuse those who come after us no end  
> because
> now we're different from every other architecture.

I introduced it because it seemed to be what was needed on parisc when
we map a kernel page on PA8800/PA8900.  We need this to ensure what the
kernel sees is up to date and also to ensure that we don't create  
inequivalent
aliases between the user and kernel mappings.

> > #define flush_kernel_dcache_range(start,size) \
> > 	flush_kernel_dcache_range_asm((start), (start)+(size));
> > /* vmap range flushes and invalidates.  Architecturally, we don't  
> > need
> > @@ -125,18 +127,27 @@ flush_anon_page(struct vm_area_struct *vma,  
> > struct page *page, unsigned long vma
> > void mark_rodata_ro(void);
> > #endif
> >
> > -#ifdef CONFIG_PA8X00
> > -/* Only pa8800, pa8900 needs this */
> > -
> > #include <asm/kmap_types.h>
> >
> > #define ARCH_HAS_KMAP
> >
> > -void kunmap_parisc(void *addr);
> > +static inline void kmap_parisc(struct page *page)
> > +{
> > +	if (parisc_requires_coherency())
> > +		flush_user_dcache_page(page);
> > +}
>
> No ... if we're genuinely moving coherency into kmap/kunmap, this  
> has to
> become
>
> 	flush_dcache_page(page);
>
> unconditionally.

There are two things about flush_dcache_page(page):

1) The flush could be deferred.  I don't think we want that.
2) It seems to unnecessarily call flush_kernel_dcache_page().

Dave
--
John David Anglin	dave.anglin@xxxxxxxx



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/