On 22/09/2023 2:40 pm, Hector Martin wrote:
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.
Apologies, I missed that apple-dart was doing something unusual here. However, could we just fix that directly instead?
diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c index 2082081402d3..0b8927508427 100644 --- a/drivers/iommu/apple-dart.c +++ b/drivers/iommu/apple-dart.c @@ -671,8 +671,7 @@ static int apple_dart_attach_dev(struct iommu_domain *domain, return ret;
switch (domain->type) { - case IOMMU_DOMAIN_DMA: - case IOMMU_DOMAIN_UNMANAGED: + default: ret = apple_dart_domain_add_streams(dart_domain, cfg); if (ret) return ret;
That's pretty much where we're headed with the domain_alloc_paging redesign anyway - at the driver level, operations on a paging domain should not need to know about the higher-level usage intent of that domain. Ideally, blocking and identity domains should have their own distinct ops now as well, but that might be a bit too big a change for an immediate fix here.
Thanks, Robin.
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,