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@lists.linux.dev Cc: stable@vger.kernel.org Fixes: a4fdd9762272 ("iommu: Use flush queue capability") Signed-off-by: Hector Martin marcan@marcan.st --- 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,