On 2023/8/22 16:24, Tian, Kevin wrote:
From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
Sent: Tuesday, August 22, 2023 2:37 PM
On 2023/8/21 14:33, Tian, Kevin wrote:
From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
Sent: Monday, August 21, 2023 1:45 PM
On 2023/8/18 11:56, Tian, Kevin wrote:
From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Sent: Monday, August 14, 2023 9:18 AM
The PASID interfaces have always supported only single-device groups.
This was first introduced in commit 26b25a2b98e45 ("iommu: Bind
process
address spaces to devices"), and has been kept consistent in
subsequent
commits.
However, the core code doesn't explicitly check for this requirement
after commit 201007ef707a8 ("PCI: Enable PASID only when ACS RR &
UF
enabled on upstream path"), which made this requirement implicit.
Restore the check to make it explicit that the PASID interfaces only
support devices belonging to single-device groups.
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/iommu/iommu.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 71b9c41f2a9e..f1eba60e573f 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3408,6 +3408,11 @@ int iommu_attach_device_pasid(struct
iommu_domain *domain,
return -ENODEV;
mutex_lock(&group->mutex);
+ if (list_count_nodes(&group->devices) != 1) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
I wonder whether we should also block adding new device to this
group once the single-device has pasid enabled. Otherwise the
This has been guaranteed by pci_enable_pasid():
if (!pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF))
return -EINVAL;
well since you are adding generic core check then it's not good to
rely on the fact of a specific bus...
We attempted to do this in the patch linked below.
https://lore.kernel.org/linux-iommu/20220705050710.2887204-5-
baolu.lu@xxxxxxxxxxxxxxx/
After long discussion, we decided to move it to the pci_enable_pasid()
interface. The non-static single device group is only relevant to PCI
fabrics that support hot-plugging without ACS support on the upstream
path.
If that's the case better add a comment to include this fact. So
another one looking at this code won't fall into the same puzzle
wondering what about a group becoming non-singleton after
above check. 😊
Yeah, fair enough.
Best regards,
baolu
