Patch "ALSA: memalloc: Don't fall back for SG-buffer with IOMMU" has been added to the 6.0-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ALSA: memalloc: Don't fall back for SG-buffer with IOMMU

to the 6.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-memalloc-don-t-fall-back-for-sg-buffer-with-iom.patch
and it can be found in the queue-6.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7173d70fe1e5d18b388590c0c73c4f5b89611f80
Author: Takashi Iwai <tiwai@xxxxxxx>
Date:   Thu Nov 10 14:22:16 2022 +0100

    ALSA: memalloc: Don't fall back for SG-buffer with IOMMU
    
    [ Upstream commit 9736a325137b62499d2b4be3fc2d742b131f75da ]
    
    When the non-contiguous page allocation for SG buffer allocation
    fails, the memalloc helper tries to fall back to the old page
    allocation methods.  This would, however, result in the bogus page
    addresses when IOMMU is enabled.  Usually in such a case, the fallback
    allocation should fail as well, but occasionally it succeeds and
    hitting a bad access.
    
    The fallback was thought for non-IOMMU case, and as the error from
    dma_alloc_noncontiguous() with IOMMU essentially implies a fatal
    memory allocation error, we should return the error straightforwardly
    without fallback.  This avoids the corner case like the above.
    
    The patch also renames the local variable "dma_ops" with snd_ prefix
    for avoiding the name conflict.
    
    Fixes: a8d302a0b770 ("ALSA: memalloc: Revive x86-specific WC page allocations again")
    Reported-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx>
    Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/alpine.DEB.2.22.394.2211041541090.3532114@xxxxxxxxxxxxxxxxxxxxxxx
    Link: https://lore.kernel.org/r/20221110132216.30605-1-tiwai@xxxxxxx
    Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
index cfcd8eff4139..2a773ed2b32a 100644
--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -9,6 +9,7 @@
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
+#include <linux/dma-map-ops.h>
 #include <linux/genalloc.h>
 #include <linux/highmem.h>
 #include <linux/vmalloc.h>
@@ -526,19 +527,20 @@ static void *snd_dma_noncontig_alloc(struct snd_dma_buffer *dmab, size_t size)
 	struct sg_table *sgt;
 	void *p;
 
-	sgt = dma_alloc_noncontiguous(dmab->dev.dev, size, dmab->dev.dir,
-				      DEFAULT_GFP, 0);
-	if (!sgt) {
 #ifdef CONFIG_SND_DMA_SGBUF
+	if (!get_dma_ops(dmab->dev.dev)) {
 		if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
 			dmab->dev.type = SNDRV_DMA_TYPE_DEV_WC_SG_FALLBACK;
 		else
 			dmab->dev.type = SNDRV_DMA_TYPE_DEV_SG_FALLBACK;
 		return snd_dma_sg_fallback_alloc(dmab, size);
-#else
-		return NULL;
-#endif
 	}
+#endif
+
+	sgt = dma_alloc_noncontiguous(dmab->dev.dev, size, dmab->dev.dir,
+				      DEFAULT_GFP, 0);
+	if (!sgt)
+		return NULL;
 
 	dmab->dev.need_sync = dma_need_sync(dmab->dev.dev,
 					    sg_dma_address(sgt->sgl));
@@ -874,7 +876,7 @@ static const struct snd_malloc_ops snd_dma_noncoherent_ops = {
 /*
  * Entry points
  */
-static const struct snd_malloc_ops *dma_ops[] = {
+static const struct snd_malloc_ops *snd_dma_ops[] = {
 	[SNDRV_DMA_TYPE_CONTINUOUS] = &snd_dma_continuous_ops,
 	[SNDRV_DMA_TYPE_VMALLOC] = &snd_dma_vmalloc_ops,
 #ifdef CONFIG_HAS_DMA
@@ -900,7 +902,7 @@ static const struct snd_malloc_ops *snd_dma_get_ops(struct snd_dma_buffer *dmab)
 	if (WARN_ON_ONCE(!dmab))
 		return NULL;
 	if (WARN_ON_ONCE(dmab->dev.type <= SNDRV_DMA_TYPE_UNKNOWN ||
-			 dmab->dev.type >= ARRAY_SIZE(dma_ops)))
+			 dmab->dev.type >= ARRAY_SIZE(snd_dma_ops)))
 		return NULL;
-	return dma_ops[dmab->dev.type];
+	return snd_dma_ops[dmab->dev.type];
 }