Messages in this thread | | | Date | Fri, 31 Aug 2012 13:47:05 +0100 | From | David Vrabel <> | Subject | Re: [Xen-devel] [PATCH 1/1] XEN: Use correct masking in xen_swiotlb_alloc_coherent. |
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On 31/08/12 10:57, Stefano Panella wrote: > When running 32-bit pvops-dom0 and a driver tries to allocate a coherent > DMA-memory the xen swiotlb-implementation returned memory beyond 4GB. > > This caused for example not working sound on a system with 4 GB and a 64-bit > compatible sound-card with sets the DMA-mask to 64bit. > > On bare-metal and the forward-ported xen-dom0 patches from OpenSuse a coherent > DMA-memory is always allocated inside the 32-bit address-range by calling > dma_alloc_coherent_mask.
We should have the same behaviour under Xen as bare metal so:
Acked-By: David Vrabel <david.vrabel@citrix.com>
This does limit the DMA mask to 32-bits by passing it through an unsigned long, which seems a bit sneaky...
Presumably the sound card is capable of handling 64 bit physical addresses (or it would break under 64-bit kernels) so it's not clear why this sound driver requires this restriction.
Is there a bug in the sound driver or sound subsystem where it's truncating a dma_addr_t by assigning it to an unsigned long or similar?
> --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -232,7 +232,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size, > return ret; > > if (hwdev && hwdev->coherent_dma_mask) > - dma_mask = hwdev->coherent_dma_mask; > + dma_mask = dma_alloc_coherent_mask(hwdev, flags);
Suggest
if (hwdev) dma_mask = dma_alloc_coherent_mask(hwdev, flags)
> phys = virt_to_phys(ret); > dev_addr = xen_phys_to_bus(phys);
David
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