If iommu_device_register() encounters an error, it can end up tearing
down already-configured groups and default domains, however this
currently still leaves devices hooked up to iommu-dma (and even
historically the behaviour in this area was at best inconsistent across
architectures/drivers...) Although in the case that an IOMMU is present
whose driver has failed to probe, users cannot necessarily expect DMA to
work anyway, it's still arguable that we should do our best to put
things back as if the IOMMU driver was never there at all, and certainly
the potential for crashing in iommu-dma itself is undesirable. Make sure
we clean up the dev->dma_iommu flag along with everything else.

Reported-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/iommu/iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index c8033ca66377..095f9e9afe8c 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -538,6 +538,9 @@ static void iommu_deinit_device(struct device *dev)
 	dev->iommu_group = NULL;
 	module_put(ops->owner);
 	dev_iommu_free(dev);
+#ifdef CONFIG_IOMMU_DMA
+	dev->dma_iommu = false;
+#endif
 }
 
 static struct iommu_domain *pasid_array_entry_to_domain(void *entry)
-- 
2.39.2.101.g768bb238c484.dirty

On Thu, Apr 10, 2025 at 12:23:48PM +0100, Robin Murphy wrote:
> Reported-by: Chen-Yu Tsai <wenst@chromium.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/iommu.c | 3 +++
>  1 file changed, 3 insertions(+)

Applied, thanks.

On Thu, Apr 10, 2025 at 7:24 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> If iommu_device_register() encounters an error, it can end up tearing
> down already-configured groups and default domains, however this
> currently still leaves devices hooked up to iommu-dma (and even
> historically the behaviour in this area was at best inconsistent across
> architectures/drivers...) Although in the case that an IOMMU is present
> whose driver has failed to probe, users cannot necessarily expect DMA to
> work anyway, it's still arguable that we should do our best to put
> things back as if the IOMMU driver was never there at all, and certainly
> the potential for crashing in iommu-dma itself is undesirable. Make sure
> we clean up the dev->dma_iommu flag along with everything else.
>
> Reported-by: Chen-Yu Tsai <wenst@chromium.org>

Closes: https://lore.kernel.org/all/CAGXv+5HJpTYmQ2h-GD7GjyeYT7bL9EBCvu0mz5LgpzJZtzfW0w@mail.gmail.com/

Tested-by: Chen-Yu Tsai <wenst@chromium.org>

> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/iommu.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index c8033ca66377..095f9e9afe8c 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -538,6 +538,9 @@ static void iommu_deinit_device(struct device *dev)
>         dev->iommu_group = NULL;
>         module_put(ops->owner);
>         dev_iommu_free(dev);
> +#ifdef CONFIG_IOMMU_DMA
> +       dev->dma_iommu = false;
> +#endif
>  }
>
>  static struct iommu_domain *pasid_array_entry_to_domain(void *entry)
> --
> 2.39.2.101.g768bb238c484.dirty
>

On 4/10/25 19:23, Robin Murphy wrote:
> If iommu_device_register() encounters an error, it can end up tearing
> down already-configured groups and default domains, however this
> currently still leaves devices hooked up to iommu-dma (and even
> historically the behaviour in this area was at best inconsistent across
> architectures/drivers...) Although in the case that an IOMMU is present
> whose driver has failed to probe, users cannot necessarily expect DMA to
> work anyway, it's still arguable that we should do our best to put
> things back as if the IOMMU driver was never there at all, and certainly
> the potential for crashing in iommu-dma itself is undesirable. Make sure
> we clean up the dev->dma_iommu flag along with everything else.
> 
> Reported-by: Chen-Yu Tsai<wenst@chromium.org>
> Signed-off-by: Robin Murphy<robin.murphy@arm.com>

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>