We change recently the memalloc helper to use
dma_alloc_noncontiguous() and the fallback to get_pages(). Although
lots of issues with IOMMU (or non-IOMMU) have been addressed, but
there seems still a regression on Xen PV. Interestingly, the only
proper way to work is use dma_alloc_coherent(). The use of
dma_alloc_coherent() for SG buffer was dropped as it's problematic on
IOMMU systems. OTOH, Xen PV has a different way, and it's fine to use
the dma_alloc_coherent().
This patch is a workaround for Xen PV. It consists of the following
changes:
- For Xen PV, use only the fallback allocation without
dma_alloc_noncontiguous()
- In the fallback allocation, use dma_alloc_coherent();
the DMA address from dma_alloc_coherent() is returned in get_addr
ops
- The DMA addresses are stored in an array; the first entry stores the
number of allocated pages in lower bits, which are referred at
releasing pages again
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Fixes: a8d302a0b7 ("ALSA: memalloc: Revive x86-specific WC page allocations again")
Fixes: 9736a32513 ("ALSA: memalloc: Don't fall back for SG-buffer with IOMMU")
Link: https://lore.kernel.org/r/87tu256lqs.wl-tiwai@suse.de
Link: https://lore.kernel.org/r/20230125153104.5527-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
53466ebdec