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SubjectRe: [PATCH] Mark i2o config broken on 64-bit platforms.
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On Wed, 2008-07-09 at 21:22 +0200, Miquel van Smoorenburg wrote:
> On Wed, 2008-07-09 at 14:13 -0500, James Bottomley wrote:
> > On Wed, 2008-07-09 at 21:06 +0200, Miquel van Smoorenburg wrote:
> > > On Wed, 2008-07-09 at 16:49 +0100, Alan Cox wrote:
> > > > On Wed, 09 Jul 2008 15:15:14 +0100
> > > > David Howells <dhowells@redhat.com> wrote:
> > > >
> > > > > Miquel van Smoorenburg <miquels@cistron.nl> wrote:
> > > > > Maybe, but have you looked at i2o_cfg_passthru()? Take this, for example:
> > > > >
> > > > > /* Allocate memory for the transfer */
> > > > > p = kmalloc(sg_size, GFP_KERNEL);
> > > > > ...
> > > > > //TODO 64bit fix
> > > > > sg[i].addr_bus = virt_to_bus(p);
> > > > >
> > > > > That looks distinctly dodgy. virt_to_bus() returns a 64-bit address, and as
> > > >
> > > > Agreed - stick | GFP_DMA32 on the end then ;)
> > >
> > > GFP_DMA32 doesn't work with kmalloc(), you need dma_alloc_coherent() or
> > > pci_alloc_consistent() [here, i2o_dma_alloc() ]
> >
> > Yes it does ... it was specifically designed for it. GFP_DMA32 was
> > introduced to allow this type of thing to happen (in the old days most
> > drivers were allowed to assume kmalloc would return memory whose
> > physical address was < 4GB; GFP_DMA32 allows that to continue while
> > allowing kmalloc to stray beyond 4GB physical).
>
> If you use alloc_pages(), yes. But not for kmalloc(). There are no
> general GFP_DMA32 slabs.

No ... it's platform specific. Platforms whose ZONE_NORMAL covers only
up to 4GB need do nothing. However, x86_64 definitely implements
ZONE_DMA32 for precisely this. Several other platforms (like ia64)
should but don't.

James




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