Commit b5031ed1 authored by Ronny Hegewald's avatar Ronny Hegewald Committed by Konrad Rzeszutek Wilk

xen: Use correct masking in xen_swiotlb_alloc_coherent.

When running 32-bit pvops-dom0 and a driver tries to allocate a coherent
DMA-memory the xen swiotlb-implementation returned memory beyond 4GB.

The underlaying reason is that if the supplied driver passes in a
DMA_BIT_MASK(64) ( hwdev->coherent_dma_mask is set to 0xffffffffffffffff)
our dma_mask will be u64 set to 0xffffffffffffffff even if we set it to
DMA_BIT_MASK(32) previously. Meaning we do not reset the upper bits.
By using the dma_alloc_coherent_mask function - it does the proper casting
and we get 0xfffffffff.

This caused 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

This patch adds the same functionality to xen swiotlb and is a rebase of the
original patch from Ronny Hegewald which never got upstream b/c the
underlaying reason was not understood until now.

The original email with the original patch is in:
the original thread from where the discussion started is in: default avatarRonny Hegewald <>
Signed-off-by: default avatarStefano Panella <>
Acked-By: default avatarDavid Vrabel <>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <>
parent ce7184bd
......@@ -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);
phys = virt_to_phys(ret);
dev_addr = xen_phys_to_bus(phys);
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