Re: [PATCH 4/4] add ksm kernel shared memory driver.

[Jeremy Fitzhardinge]

Andrea Arcangeli wrote:
> On Wed, Apr 15, 2009 at 05:43:03PM -0700, Jeremy Fitzhardinge wrote:
>   
> > Shouldn't that be kmap_atomic's job anyway?  Otherwise it would be hard to 
> >     
>
> No because those are full noops in no-highmem kernels. I commented in
> other email why I think it's safe thanks to the wrprotect + smp tlb
> flush of the userland PTE.
>   

I think Andrew's query was about data cache synchronization in 
architectures with virtually indexed d-cache.  On x86 it's a non-issue, 
but on architectures for which it is an issue, I assume kmap_atomic does 
any necessary cache flushes, as it does tlb flushes on x86 (which may be 
none at all, if no mapping actually happens).

   J

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