linux-kernel - [PATCH] iommu/s390: tolerate repeat attach

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Message-Id: <20220519182929.581898-1-mjrosato@linux.ibm.com>
Date:   Thu, 19 May 2022 14:29:29 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     jgg@...dia.com, joro@...tes.org
Cc:     will@...nel.org, alex.williamson@...hat.com, cohuck@...hat.com,
        borntraeger@...ux.ibm.com, schnelle@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, farman@...ux.ibm.com,
        iommu@...ts.linux-foundation.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/s390: tolerate repeat attach_dev calls

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 <mjrosato@...ux.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