> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Monday, May 15, 2023 10:00 PM
>
> Replace allows all the devices in a group to move in one step to a new
> HWPT. Further, the HWPT move is done without going through a blocking
> domain so that the IOMMU driver can implement some level of
> non-distruption to ongoing DMA if that has meaning for it (eg for future
> special driver domains)
>
> Replace uses a lot of the same logic as normal attach, except the actual
> domain change over has different restrictions, and we are careful to
> sequence things so that failure is going to leave everything the way it
> was, and not get trapped in a blocking domain or something if there is
> ENOMEM.
>
> Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
> drivers/iommu/iommufd/device.c | 99 ++++++++++++++++++++++++++++++++++
> drivers/iommu/iommufd/main.c | 1 +
> 2 files changed, 100 insertions(+)
>
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index b7868c877d1c1c..ce758fbe3c525d 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -4,6 +4,7 @@
> #include <linux/iommufd.h>
> #include <linux/slab.h>
> #include <linux/iommu.h>
> +#include "../iommu-priv.h"
>
> #include "io_pagetable.h"
> #include "iommufd_private.h"
> @@ -365,6 +366,84 @@ iommufd_device_do_attach(struct iommufd_device *idev,
> return NULL;
> }
>
> +static struct iommufd_hw_pagetable *
> +iommufd_device_do_replace(struct iommufd_device *idev,
> + struct iommufd_hw_pagetable *hwpt)
> +{
> + struct iommufd_group *igroup = idev->igroup;
> + struct iommufd_hw_pagetable *old_hwpt;
> + unsigned int num_devices = 0;
> + struct iommufd_device *cur;
> + int rc;
> +
> + mutex_lock(&idev->igroup->lock);
> +
> + if (igroup->hwpt == NULL) {
> + rc = -EINVAL;
> + goto err_unlock;
> + }
> +
> + if (hwpt == igroup->hwpt) {
> + mutex_unlock(&idev->igroup->lock);
> + return NULL;
> + }
> +
> + /* Try to upgrade the domain we have */
> + list_for_each_entry(cur, &igroup->device_list, group_item) {
> + num_devices++;
> + if (cur->enforce_cache_coherency) {
> + rc = iommufd_hw_pagetable_enforce_cc(hwpt);
> + if (rc)
> + goto err_unlock;
> + }
> + }
> +
> + old_hwpt = igroup->hwpt;
> + if (hwpt->ioas != old_hwpt->ioas) {
> + list_for_each_entry(cur, &igroup->device_list, group_item) {
> + rc = iopt_table_enforce_dev_resv_regions(
> + &hwpt->ioas->iopt, cur->dev, NULL);
> + if (rc)
> + goto err_unresv;
> + }
> + }
> +
> + rc = iommufd_group_setup_msi(idev->igroup, hwpt);
> + if (rc)
> + goto err_unresv;
> +
> + rc = iommu_group_replace_domain(igroup->group, hwpt->domain);
> + if (rc)
> + goto err_unresv;
> +
> + if (hwpt->ioas != old_hwpt->ioas) {
> + list_for_each_entry(cur, &igroup->device_list, group_item)
> + iopt_remove_reserved_iova(&old_hwpt->ioas->iopt,
> + cur->dev);
> + }
> +
> + igroup->hwpt = hwpt;
> +
> + /*
> + * Move the refcounts held by the device_list to the new hwpt. Retain a
> + * refcount for this thread as the caller will free it.
> + */
> + refcount_add(num_devices, &hwpt->obj.users);
> + if (num_devices > 1)
> + WARN_ON(refcount_sub_and_test(num_devices - 1,
> + &old_hwpt->obj.users));
> + mutex_unlock(&idev->igroup->lock);
> +
> + /* Caller must destroy old_hwpt */
> + return old_hwpt;
> +err_unresv:
> + list_for_each_entry(cur, &igroup->device_list, group_item)
> + iopt_remove_reserved_iova(&hwpt->ioas->iopt, cur->dev);
> +err_unlock:
> + mutex_unlock(&idev->igroup->lock);
> + return ERR_PTR(rc);
> +}
> +
> typedef struct iommufd_hw_pagetable *(*attach_fn)(
> struct iommufd_device *idev, struct iommufd_hw_pagetable *hwpt);
>
> @@ -523,6 +602,26 @@ int iommufd_device_attach(struct iommufd_device *idev, u32
> *pt_id)
> }
> EXPORT_SYMBOL_NS_GPL(iommufd_device_attach, IOMMUFD);
>
> +/**
> + * iommufd_device_replace - Change the device's iommu_domain
> + * @idev: device to change
> + * @pt_id: Input a IOMMUFD_OBJ_IOAS, or IOMMUFD_OBJ_HW_PAGETABLE
> + * Output the IOMMUFD_OBJ_HW_PAGETABLE ID
> + *
> + * This is the same as
> + * iommufd_device_detach();
> + * iommufd_device_attach();
One blank line here would fix a warning as below in "make htmldocs".
Documentation/userspace-api/iommufd:184: ./drivers/iommu/iommufd/device.c:665: WARNING: Definition list ends without a blank line; unexpected unindent.
Regards,
Yi Liu
> + * If it fails then no change is made to the attachment. The iommu driver may
> + * implement this so there is no disruption in translation. This can only be
> + * called if iommufd_device_attach() has already succeeded.
> + */
> +int iommufd_device_replace(struct iommufd_device *idev, u32 *pt_id)
> +{
> + return iommufd_device_change_pt(idev, pt_id,
> + &iommufd_device_do_replace);
> +}
> +EXPORT_SYMBOL_NS_GPL(iommufd_device_replace, IOMMUFD);
> +
> /**
> * iommufd_device_detach - Disconnect a device to an iommu_domain
> * @idev: device to detach
> diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
> index 24f30f384df6f9..5b7f70543adb24 100644
> --- a/drivers/iommu/iommufd/main.c
> +++ b/drivers/iommu/iommufd/main.c
> @@ -466,5 +466,6 @@ module_exit(iommufd_exit);
> MODULE_ALIAS_MISCDEV(VFIO_MINOR);
> MODULE_ALIAS("devname:vfio/vfio");
> #endif
> +MODULE_IMPORT_NS(IOMMUFD_INTERNAL);
> MODULE_DESCRIPTION("I/O Address Space Management for passthrough devices");
> MODULE_LICENSE("GPL");
> --
> 2.40.1
