Hi,
On 27/04/2022 17:15, Rahul Singh wrote:
When a device is deassigned from the domain it is required to remove the
iommu group.
This read wrong to me. We should not need to re-create the IOMMU group
(and call arm_smmu_add_device()) every time a device is re-assigned.
If we don't remove the group, the next time when we assign
a device, SME and S2CR will not be setup correctly for the device
because of that SMMU fault will be observed.
I think this is a bug fix for 0435784cc75dcfef3b5f59c29deb1dbb84265ddb.
If so, please add a Fixes tag.
Signed-off-by: Rahul Singh <[email protected]>
---
xen/drivers/passthrough/arm/smmu.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/xen/drivers/passthrough/arm/smmu.c
b/xen/drivers/passthrough/arm/smmu.c
index 5cacb2dd99..9a31c332d0 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -1690,6 +1690,8 @@ static void arm_smmu_detach_dev(struct iommu_domain
*domain, struct device *dev)
if (cfg)
arm_smmu_master_free_smes(cfg);
+ iommu_group_put(dev_iommu_group(dev));
+ dev_iommu_group(dev) = NULL;
}
The goal of arm_smmu_detach_dev() is to revert the change made in
arm_smmu_attach_dev(). But looking at the code, neither the IOMMU group
nor the smes are allocated in arm_smmu_attach_dev().
Are the SMES meant to be re-allocated everytime we assign to a different
domain? If yes, the allocation should be done in arm_smmu_attach_dev().
If not, then we should not free the SMES here
IIUC, the SMES have to be re-allocated every time a device is assigned.
Therefore, I think we should move the call to
arm_smmu_master_alloc_smes() out of the detach callback and in a helper
that would be used when removing a device (not yet supported by Xen).
Cheers,
--
Julien Grall
