From: Jason Gunthorpe <jgg@xxxxxxxxxx>
Sent: Tuesday, January 16, 2024 8:58 PM
On Tue, Jan 16, 2024 at 01:18:12AM +0000, Tian, Kevin wrote:
idev/pasidFrom: Jason Gunthorpe <jgg@xxxxxxxxxx>
Sent: Tuesday, January 16, 2024 1:25 AM
On Sun, Nov 26, 2023 at 10:34:23PM -0800, Yi Liu wrote:
+/**iommu_domain
+ * iommufd_device_pasid_detach - Disconnect a {device, pasid} to an
+ * @idev: device to detach
+ * @pasid: pasid to detach
+ *
+ * Undo iommufd_device_pasid_attach(). This disconnects the
from
+ * the previously attached pt_id.pasid)
+ */
+void iommufd_device_pasid_detach(struct iommufd_device *idev, u32
+{
+ struct iommufd_hw_pagetable *hwpt;
+
+ hwpt = xa_load(&idev->pasid_hwpts, pasid);
+ if (!hwpt)
+ return;
+ xa_erase(&idev->pasid_hwpts, pasid);
+ iommu_detach_device_pasid(hwpt->domain, idev->dev, pasid);
+ iommufd_hw_pagetable_put(idev->ictx, hwpt);
+}
None of this xarray stuff looks locked properly
I had an impression from past discussions that the caller should not
race attach/detach/replace on same device or pasid, otherwise it is
already a problem in a higher level.
I thought that was just at the iommu layer? We want VFIO to do the
same? Then why do we need the dual xarrays?
Still, it looks really wrong to have code like this, we don't need to
- it can be locked properly, it isn't a performance path..
OK, let's add a lock for this.
and the original intention of the group lock was to ensure all devices
in the group have a same view. Not exactly to guard concurrent
attach/detach.
We don't have a group lock here, this is in iommufd.
I meant the lock in iommufd_group.
Use the xarray lock..
eg
hwpt = xa_erase(&idev->pasid_hwpts, pasid);
if (WARN_ON(!hwpt))
return
xa_erase is atomic.
yes, that's better.