From: Logan Gunthorpe <logang@deltatee.com>
Date: Wed, 27 Oct 2021 11:47:57 -0600
Subject: iommu/dma: Fix incorrect error return on iommu deferred attach
Git-commit: ac315f96b3bd6f6b8f18f387816c7c2cc6b32e02
Patch-mainline: v5.16-rc1
References: bsc#1205701

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 <marshallmidden@gmail.com>
Fixes: dabb16f67215 ("iommu/dma: return error code from iommu_dma_map_sg()")
Link: https://lore.kernel.org/all/CAD2CkAWjS8=kKwEEN4cgVNjyFORUibzEiCUA-X+SMtbo0JoMmA@mail.gmail.com
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20211027174757.119755-1-logang@deltatee.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/dma-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

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))