Re: [PATCH v2 2/7] iommu: Add reset_device_done callback for hardware fault recovery

[Baolu Lu <baolu.lu@linux.intel.com>]

On 3/18/26 03:15, Nicolin Chen wrote:
> When an IOMMU hardware detects an error due to a faulty device (e.g. an ATS
> invalidation timeout), IOMMU drivers may quarantine the device by disabling
> specific hardware features or dropping translation capabilities.
> 
> To recover from these states, the IOMMU driver needs a reliable signal that
> the underlying physical hardware has been cleanly reset (e.g., via PCIe AER
> or a sysfs Function Level Reset) so as to lift the quarantine.
> 
> Introduce a reset_device_done callback in struct iommu_ops. Trigger it from
> the existing pci_dev_reset_iommu_done() path to notify the underlying IOMMU
> driver that the device's internal state has been sanitized.
> 
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>   include/linux/iommu.h |  2 ++
>   drivers/iommu/iommu.c | 12 ++++++++++++
>   2 files changed, 14 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 54b8b48c762e8..9ba12b2164724 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -626,6 +626,7 @@ __iommu_copy_struct_to_user(const struct iommu_user_data *dst_data,
>    * @release_device: Remove device from iommu driver handling
>    * @probe_finalize: Do final setup work after the device is added to an IOMMU
>    *                  group and attached to the groups domain
> + * @reset_device_done: Notify the driver about the completion of a device reset
>    * @device_group: find iommu group for a particular device
>    * @get_resv_regions: Request list of reserved regions for a device
>    * @of_xlate: add OF master IDs to iommu grouping
> @@ -683,6 +684,7 @@ struct iommu_ops {
>   	struct iommu_device *(*probe_device)(struct device *dev);
>   	void (*release_device)(struct device *dev);
>   	void (*probe_finalize)(struct device *dev);
> +	void (*reset_device_done)(struct device *dev);
>   	struct iommu_group *(*device_group)(struct device *dev);
>   
>   	/* Request/Free a list of reserved regions for a device */
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 40a15c9360bd1..fcd2902d9e8db 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -4013,11 +4013,13 @@ EXPORT_SYMBOL_GPL(pci_dev_reset_iommu_prepare);
>   void pci_dev_reset_iommu_done(struct pci_dev *pdev)
>   {
>   	struct iommu_group *group = pdev->dev.iommu_group;
> +	const struct iommu_ops *ops;
>   	unsigned long pasid;
>   	void *entry;
>   
>   	if (!pci_ats_supported(pdev) || !dev_has_iommu(&pdev->dev))
>   		return;
> +	ops = dev_iommu_ops(&pdev->dev);
>   
>   	guard(mutex)(&group->mutex);
>   
> @@ -4029,6 +4031,16 @@ void pci_dev_reset_iommu_done(struct pci_dev *pdev)
>   	if (WARN_ON(!group->blocking_domain))
>   		return;
>   
> +	/*
> +	 * A PCI device might have been in an error state, so the IOMMU driver
> +	 * had to quarantine the device by disabling specific hardware feature
> +	 * or dropping translation capability. Here notify the IOMMU driver as
> +	 * a reliable signal that the faulty PCI device has been cleanly reset
> +	 * so now it can lift its quarantine and restore full functionality.
> +	 */
> +	if (ops && ops->reset_device_done)
> +		ops->reset_device_done(&pdev->dev);

Nit: dev_iommu_ops() ensures a valid iommu "ops". There is no need to
check "ops != NULL" here. Just

	if (ops->reset_device_done)
		ops->reset_device_done(&pdev->dev);

> +
>   	/* Re-attach RID domain back to group->domain */
>   	if (group->domain != group->blocking_domain) {
>   		WARN_ON(__iommu_attach_device(group->domain, &pdev->dev,

Thanks,
baolu