scsi_dma_map() was reporting a failure during boot on an AMD machine
with the IOMMU enabled.

  scsi_dma_map failed: request for 36 bytes!

The issue was tracked down to a mistake in logic: should not return
an error if iommu_deferred_attach() returns zero.

Reported-by: Marshall Midden <marshallmid...@gmail.com>
Fixes: dabb16f67215 ("iommu/dma: return error code from iommu_dma_map_sg()")
Link: 
https://lore.kernel.org/all/CAD2CkAWjS8=kkween4cgvnjyforuibzeicua-x+smtbo0jo...@mail.gmail.com
Signed-off-by: Logan Gunthorpe <log...@deltatee.com>
Cc: Joerg Roedel <j...@8bytes.org>
Cc: Will Deacon <w...@kernel.org>
---
 drivers/iommu/dma-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

If possible, this fix should really get into Linus's tree before the
v5.15 release.

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 896bea04c347..3e5a21b0bb24 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1016,7 +1016,8 @@ static int iommu_dma_map_sg(struct device *dev, struct 
scatterlist *sg,

        if (static_branch_unlikely(&iommu_deferred_attach_enabled)) {
                ret = iommu_deferred_attach(dev, domain);
-               goto out;
+               if (ret)
+                       goto out;
        }

        if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))

base-commit: 3906fe9bb7f1a2c8667ae54e967dc8690824f4ea
--
2.30.2
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