ALSA: memalloc: Use proper DMA mapping API for x86 S/G buffer allocat…

…ions

The fallback S/G buffer allocation for x86 used the addresses deduced
from the page allocations blindly.  It broke the allocations on IOMMU
and made us to work around with a hackish DMA ops check.

For cleaning up those messes, this patch switches to the proper DMA
mapping API usages with the standard sg-table instead.

By introducing the sg-table, the address table isn't needed, but for
keeping the original allocation sizes for freeing, replace it with the
array keeping the number of pages.

The get_addr callback is changed to use the existing one for
non-contiguous buffers.  (Also it's the reason sg_table is put at the
beginning of struct snd_dma_sg_fallback.)

And finally, the hackish workaround that checks the DMA ops is
dropped now.

Link: https://patch.msgid.link/20240912155227.4078-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/memalloc.c

@@ -680,43 +680,43 @@ static const struct snd_malloc_ops snd_dma_noncontig_ops = {
 #ifdef CONFIG_SND_DMA_SGBUF
 /* Fallback SG-buffer allocations for x86 */
 struct snd_dma_sg_fallback {
+ struct sg_table sgt; /* used by get_addr - must be the first item */
  size_t count;
  struct page **pages;
- /* DMA address array; the first page contains #pages in ~PAGE_MASK */
- dma_addr_t *addrs;
+ unsigned int *npages;
 };
 
 static void __snd_dma_sg_fallback_free(struct snd_dma_buffer *dmab,
  struct snd_dma_sg_fallback *sgbuf)
 {
+ bool wc = dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG;
  size_t i, size;
 
- if (sgbuf->pages && sgbuf->addrs) {
+ if (sgbuf->pages && sgbuf->npages) {
  i = 0;
  while (i < sgbuf->count) {
- if (!sgbuf->pages[i] || !sgbuf->addrs[i])
- break;
- size = sgbuf->addrs[i] & ~PAGE_MASK;
- if (WARN_ON(!size))
+ size = sgbuf->npages[i];
+ if (!size)
  break;
  do_free_pages(page_address(sgbuf->pages[i]),
- size << PAGE_SHIFT, false);
+ size << PAGE_SHIFT, wc);
  i += size;
  }
  }
  kvfree(sgbuf->pages);
- kvfree(sgbuf->addrs);
+ kvfree(sgbuf->npages);
  kfree(sgbuf);
 }
 
 /* fallback manual S/G buffer allocations */
 static void *snd_dma_sg_fallback_alloc(struct snd_dma_buffer *dmab, size_t size)
 {
+ bool wc = dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG;
  struct snd_dma_sg_fallback *sgbuf;
  struct page **pagep, *curp;
- size_t chunk, npages;
- dma_addr_t *addrp;
+ size_t chunk;
  dma_addr_t addr;
+ unsigned int idx, npages;
  void *p;
 
  sgbuf = kzalloc(sizeof(*sgbuf), GFP_KERNEL);
@@ -725,16 +725,16 @@ static void *snd_dma_sg_fallback_alloc(struct snd_dma_buffer *dmab, size_t size)
  size = PAGE_ALIGN(size);
  sgbuf->count = size >> PAGE_SHIFT;
  sgbuf->pages = kvcalloc(sgbuf->count, sizeof(*sgbuf->pages), GFP_KERNEL);
- sgbuf->addrs = kvcalloc(sgbuf->count, sizeof(*sgbuf->addrs), GFP_KERNEL);
- if (!sgbuf->pages || !sgbuf->addrs)
+ sgbuf->npages = kvcalloc(sgbuf->count, sizeof(*sgbuf->npages), GFP_KERNEL);
+ if (!sgbuf->pages || !sgbuf->npages)
  goto error;
 
  pagep = sgbuf->pages;
- addrp = sgbuf->addrs;
- chunk = (PAGE_SIZE - 1) << PAGE_SHIFT; /* to fit in low bits in addrs */
+ chunk = size;
+ idx = 0;
  while (size > 0) {
  chunk = min(size, chunk);
- p = do_alloc_pages(dmab->dev.dev, chunk, &addr, false);
+ p = do_alloc_pages(dmab->dev.dev, chunk, &addr, wc);
  if (!p) {
  if (chunk <= PAGE_SIZE)
  goto error;
@@ -746,27 +746,33 @@ static void *snd_dma_sg_fallback_alloc(struct snd_dma_buffer *dmab, size_t size)
  size -= chunk;
  /* fill pages */
  npages = chunk >> PAGE_SHIFT;
- *addrp = npages; /* store in lower bits */
+ sgbuf->npages[idx] = npages;
+ idx += npages;
  curp = virt_to_page(p);
- while (npages--) {
+ while (npages--)
  *pagep++ = curp++;
- *addrp++ |= addr;
- addr += PAGE_SIZE;
- }
  }
 
- p = vmap(sgbuf->pages, sgbuf->count, VM_MAP, PAGE_KERNEL);
- if (!p)
+ if (sg_alloc_table_from_pages(&sgbuf->sgt, sgbuf->pages, sgbuf->count,
+  0, sgbuf->count << PAGE_SHIFT, GFP_KERNEL))
  goto error;
 
- if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
- set_pages_array_wc(sgbuf->pages, sgbuf->count);
+ if (dma_map_sgtable(dmab->dev.dev, &sgbuf->sgt, DMA_BIDIRECTIONAL, 0))
+ goto error_dma_map;
+
+ p = vmap(sgbuf->pages, sgbuf->count, VM_MAP, PAGE_KERNEL);
+ if (!p)
+ goto error_vmap;
 
  dmab->private_data = sgbuf;
  /* store the first page address for convenience */
- dmab->addr = sgbuf->addrs[0] & PAGE_MASK;
+ dmab->addr = snd_sgbuf_get_addr(dmab, 0);
  return p;
 
+ error_vmap:
+ dma_unmap_sgtable(dmab->dev.dev, &sgbuf->sgt, DMA_BIDIRECTIONAL, 0);
+ error_dma_map:
+ sg_free_table(&sgbuf->sgt);
  error:
  __snd_dma_sg_fallback_free(dmab, sgbuf);
  return NULL;
@@ -776,21 +782,12 @@ static void snd_dma_sg_fallback_free(struct snd_dma_buffer *dmab)
 {
  struct snd_dma_sg_fallback *sgbuf = dmab->private_data;
 
- if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
- set_pages_array_wb(sgbuf->pages, sgbuf->count);
  vunmap(dmab->area);
+ dma_unmap_sgtable(dmab->dev.dev, &sgbuf->sgt, DMA_BIDIRECTIONAL, 0);
+ sg_free_table(&sgbuf->sgt);
  __snd_dma_sg_fallback_free(dmab, dmab->private_data);
 }
 
-static dma_addr_t snd_dma_sg_fallback_get_addr(struct snd_dma_buffer *dmab,
- size_t offset)
-{
- struct snd_dma_sg_fallback *sgbuf = dmab->private_data;
- size_t index = offset >> PAGE_SHIFT;
-
- return (sgbuf->addrs[index] & PAGE_MASK) | (offset & ~PAGE_MASK);
-}
-
 static int snd_dma_sg_fallback_mmap(struct snd_dma_buffer *dmab,
  struct vm_area_struct *area)
 {
@@ -816,18 +813,15 @@ static void *snd_dma_sg_alloc(struct snd_dma_buffer *dmab, size_t size)
  return p;
 
  dmab->dev.type = type; /* restore the type */
- /* if IOMMU is present but failed, give up */
- if (get_dma_ops(dmab->dev.dev))
- return NULL;
- /* try fallback */
  return snd_dma_sg_fallback_alloc(dmab, size);
 }
 
 static const struct snd_malloc_ops snd_dma_sg_ops = {
  .alloc = snd_dma_sg_alloc,
  .free = snd_dma_sg_fallback_free,
  .mmap = snd_dma_sg_fallback_mmap,
- .get_addr = snd_dma_sg_fallback_get_addr,
+ /* reuse noncontig helper */
+ .get_addr = snd_dma_noncontig_get_addr,
  /* reuse vmalloc helpers */
  .get_page = snd_dma_vmalloc_get_page,
  .get_chunk_size = snd_dma_vmalloc_get_chunk_size,