Messages in this thread | | | Date | 24 Jun 2004 12:33:18 +0200 | Date | Thu, 24 Jun 2004 12:33:18 +0200 | From | Andi Kleen <> | Subject | Re: 32-bit dma allocations on 64-bit platforms |
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On Thu, Jun 24, 2004 at 08:18:06AM +0200, Arjan van de Ven wrote: > On Wed, 2004-06-23 at 23:46, Andi Kleen wrote: > > > The VM should be able to handle this, but it may still require > > some tuning. It would need some generic changes, but not too bad. > > Still would need a decision on how big GFP_BIGDMA should be. > > I suspect 4GB would be too big again. > > What is the problem again, can't the driver us the dynamic pci mapping > API which does allow more memory to be mapped even on crippled machines > without iommu ?
In theory one could fix pci_alloc_consistent from the swiotlb pool yes, the problem is just that this pool is completely preallocated. If enough memory is needed that would be quite nasty, because you suddenly lose 1 or 2GB RAM.
> And isn't this a problem that will vanish since PCI Express and PCI X > both *require* support for 64 bit addressing, so all higher speed cards > are going to be ok in principle ?
There are EM64T systems with AGP only and not all PCI-Express cards seem to follow this. PCI-Express unfortunately discouraged the AGP aperture too, so not even that can be used on those Intel systems.
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