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Date: Wed, 2 Oct 2002 11:18:09 +1000
From: David Gibson <david@gibson.dropbear.id.au>
To: Russell King <rmk@arm.linux.org.uk>
Cc: Andrew Morton <akpm@digeo.com>, David Miller <davem@redhat.com>,
       Paul Mackerras <paulus@samba.org>, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH,RFC] Add gfp_mask to get_vm_area()
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On Tue, Oct 01, 2002 at 09:42:02AM +0100, Russell King wrote:
> 
> On Tue, Oct 01, 2002 at 03:34:17PM +1000, David Gibson wrote:
> > I don't see an easy one: PPC 4xx has non-coherent cache, so we have to
> > mark consistent memory non-cacheable.  We want to make the normal
> > lowmem mapping use large page TLB entries, so we can't frob the
> > attribute bits on the pages in place.  That means we need to create a
> > new, non-cacheable mapping for the physical RAM we allocate, which in
> > turn means allocating a chunk of kernel virtual memory.
> 
> Same problem on ARM.  I just haven't got the motivation to rewrite the
> bits of the kernel that need to be rewritten to make it work.
> 
> Have you checked that your pte/pmd allocation functions can be called
> from IRQ context as well?
> 
> You basically need:
> 
>  - irq-safe get_vm_area
>  - irq-safe pmd_alloc_kernel
>  - irq-safe pte_alloc_kernel
> 
> Last time I looked, all the above were not irq-safe.

No, I realise they're not safe at the moment - I'm working on that
too.

-- 
David Gibson			| For every complex problem there is a
david@gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson