[PATCH] iommu/s390: tolerate repeat attach_dev calls

[Matthew Rosato]

Since commit 0286300e6045 ("iommu: iommu_group_claim_dma_owner() must
always assign a domain") s390-iommu will get called to allocate multiple
unmanaged iommu domains for a vfio-pci device -- however the current
s390-iommu logic tolerates only one.  Recognize that multiple domains can
be allocated and handle switching between DMA or different iommu domain
tables during attach_dev.

Signed-off-by: Matthew Rosato <mjros...@linux.ibm.com>
---
 drivers/iommu/s390-iommu.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 3833e86c6e7b..c898bcbbce11 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -99,7 +99,7 @@ static int s390_iommu_attach_device(struct iommu_domain 
*domain,
        if (!domain_device)
                return -ENOMEM;
 
-       if (zdev->dma_table) {
+       if (zdev->dma_table && !zdev->s390_domain) {
                cc = zpci_dma_exit_device(zdev);
                if (cc) {
                        rc = -EIO;
@@ -107,6 +107,9 @@ static int s390_iommu_attach_device(struct iommu_domain 
*domain,
                }
        }
 
+       if (zdev->s390_domain)
+               zpci_unregister_ioat(zdev, 0);
+
        zdev->dma_table = s390_domain->dma_table;
        cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
                                virt_to_phys(zdev->dma_table));
@@ -136,7 +139,13 @@ static int s390_iommu_attach_device(struct iommu_domain 
*domain,
        return 0;
 
 out_restore:
-       zpci_dma_init_device(zdev);
+       if (!zdev->s390_domain) {
+               zpci_dma_init_device(zdev);
+       } else {
+               zdev->dma_table = zdev->s390_domain->dma_table;
+               zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
+                                  virt_to_phys(zdev->dma_table));
+       }
 out_free:
        kfree(domain_device);
 
@@ -167,7 +176,7 @@ static void s390_iommu_detach_device(struct iommu_domain 
*domain,
        }
        spin_unlock_irqrestore(&s390_domain->list_lock, flags);
 
-       if (found) {
+       if (found && (zdev->s390_domain == s390_domain)) {
                zdev->s390_domain = NULL;
                zpci_unregister_ioat(zdev, 0);
                zpci_dma_init_device(zdev);
-- 
2.27.0

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