[PATCH 5.12 256/296] iommu/amd: Clear DMA ops when switching domain

Greg Kroah-Hartman
2021-05-31T16:47:02Z

From: Jean-Philippe Brucker <jean-philippe@linaro.org>

[ Upstream commit d6177a6556f853785867e2ec6d5b7f4906f0d809 ]

Since commit 08a27c1c3ecf ("iommu: Add support to change default domain
of an iommu group") a user can switch a device between IOMMU and direct
DMA through sysfs. This doesn't work for AMD IOMMU at the moment because
dev->dma_ops is not cleared when switching from a DMA to an identity
IOMMU domain. The DMA layer thus attempts to use the dma-iommu ops on an
identity domain, causing an oops:

# echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/unbind
# echo identity > /sys/bus/pci/devices/0000:00:05.0/iommu_group/type
# echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/bind
...
BUG: kernel NULL pointer dereference, address: 0000000000000028
...
Call Trace:
iommu_dma_alloc
e1000e_setup_tx_resources
e1000e_open

Since iommu_change_dev_def_domain() calls probe_finalize() again, clear
the dma_ops there like Vt-d does.

Fixes: 08a27c1c3ecf ("iommu: Add support to change default domain of an iommu group")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20210422094216.2282097-1-jean-philippe@linaro.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/amd/iommu.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index a69a8b573e40..7de7a260706b 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -1747,6 +1747,8 @@ static void amd_iommu_probe_finalize(struct device *dev)
domain = iommu_get_domain_for_dev(dev);
if (domain->type == IOMMU_DOMAIN_DMA)
iommu_setup_dma_ops(dev, IOVA_START_PFN << PAGE_SHIFT, 0);
+ else
+ set_dma_ops(dev, NULL);
}

static void amd_iommu_release_device(struct device *dev)
--
2.30.2