linux-kernel - [PATCH] iommu/dma: fix incorrect error return on iommu deferred attach

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Date:   Wed, 27 Oct 2021 11:47:57 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Christoph Hellwig <hch@....de>
Cc:     Logan Gunthorpe <logang@...tatee.com>,
        Marshall Midden <marshallmidden@...il.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Subject: [PATCH] iommu/dma: fix incorrect error return on iommu deferred attach

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@...il.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@...tatee.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Will Deacon <will@...nel.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