Commit a4fdd9762272 ("iommu: Use flush queue capability") hid the
IOMMU_DOMAIN_DMA_FQ domain type from domain allocation. A check was
introduced in iommu_dma_init_domain() to fall back if not supported, but
this check runs too late: by that point, devices have been attached to
the IOMMU, and the IOMMU driver might not expect FQ domains at
ops->attach_dev() time.
Ensure that we immediately clamp FQ domains to plain DMA if not
supported by the driver at device attach time, not later.
This regressed apple-dart in v6.5.
Cc: regressions@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: a4fdd9762272 ("iommu: Use flush queue capability")
Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
---
drivers/iommu/iommu.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3bfc56df4f78..12464eaa8d91 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2039,6 +2039,15 @@ static int __iommu_attach_device(struct iommu_domain *domain,
if (unlikely(domain->ops->attach_dev == NULL))
return -ENODEV;
+ /*
+ * Ensure we do not try to attach devices to FQ domains if the
+ * IOMMU does not support them. We can safely fall back to
+ * non-FQ.
+ */
+ if (domain->type == IOMMU_DOMAIN_DMA_FQ &&
+ !device_iommu_capable(dev, IOMMU_CAP_DEFERRED_FLUSH))
+ domain->type = IOMMU_DOMAIN_DMA;
+
ret = domain->ops->attach_dev(domain, dev);
if (ret)
return ret;
---
base-commit: ce9ecca0238b140b88f43859b211c9fdfd8e5b70
change-id: 20230922-iommu-type-regression-25b4f43df770
Best regards,
--
Hector Martin <marcan@xxxxxxxxx>
