Messages in this thread | | | Date | Thu, 9 Apr 2009 07:10:32 +0900 | Subject | Re: [PATCH 4/7] swiotlb: Allow arch override of address_needs_mapping | From | FUJITA Tomonori <> |
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On Wed, 08 Apr 2009 14:55:55 -0700 Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> FUJITA Tomonori wrote: > > On Wed, 8 Apr 2009 15:56:32 -0500 > > Kumar Gala <galak@kernel.crashing.org> wrote: > > > > > >> On Apr 8, 2009, at 3:38 PM, Christoph Hellwig wrote: > >> > >> > >>> On Wed, Apr 08, 2009 at 09:09:18AM -0500, Kumar Gala wrote: > >>> > >>>> From: Becky Bruce <beckyb@kernel.crashing.org> > >>>> > >>>> Some architectures require additional checking to determine > >>>> if a device can dma to an address and need to provide their > >>>> own address_needs_mapping.. > >>>> > >>> Shouldn't we just move it completely to the arch? I think that ia64 > >>> and > >>> x86 currently use the same one is more of an accident. > >>> > >> It seems like the swiotlb code uses __weak for a number of things: > >> > >> lib/swiotlb.c:void * __weak __init swiotlb_alloc_boot(size_t size, > >> unsigned long nslabs) > >> lib/swiotlb.c:void * __weak swiotlb_alloc(unsigned order, unsigned > >> long nslabs) > >> lib/swiotlb.c:dma_addr_t __weak swiotlb_phys_to_bus(struct device > >> *hwdev, phys_addr_t paddr) > >> lib/swiotlb.c:phys_addr_t __weak swiotlb_bus_to_phys(struct device > >> *hwdev, dma_addr_t baddr) > >> lib/swiotlb.c:void * __weak swiotlb_bus_to_virt(struct device *hwdev, > >> dma_addr_t address) > >> lib/swiotlb.c:int __weak swiotlb_arch_address_needs_mapping(struct > >> device *hwdev, > >> lib/swiotlb.c:int __weak swiotlb_arch_range_needs_mapping(phys_addr_t > >> paddr, size_t size) > >> > >> instead of #ifndef HAVE_ARCH_<FOO>. Not sure if there is a historical > >> reason for that. > >> > > > > ia64 and x86_64 use swiotlb but neither need this function. And > > neither need any above __weak. They were added for dom0 support. > > Yeah, swiotlb is much cleaner and better if we don't add dom0 support. > > > > Some architectures need non-trivial bus<->phys conversion routines, etc,
Only Xen needs such conversion for swiotlb.
> so either we can require it that all architectures wishing to use > swiotlb define these functions, or have weak default functions that can > be overridden by architectures where necessary.
Can you give an example? I don't think IA64, X86_64 or POWER (which will use swiotlb) need any __weak functions. If you say other archs could use swiotlb, please tell me how they need these __weak.
> This isn't a specific Xen dom0 requirement, except that enabling it in
Yes, it is.
> the config will override these functions (but now in a Xen-only file, > rather than affecting the normal x86 pci-swiotlb.c).
And again, x86' pci-swiotlb is much cleaner without dom0 support.
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