linux-kernel - [PATCH 1/2] powerpc: iommu: Bring back table group release

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Date: Thu, 25 Jan 2024 06:08:39 -0600
From: Shivaprasad G Bhat <sbhat@...ux.ibm.com>
To: iommu@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org, mpe@...erman.id.au, npiggin@...il.com,
        christophe.leroy@...roup.eu, aneesh.kumar@...nel.org,
        naveen.n.rao@...ux.ibm.com, jgg@...pe.ca, jroedel@...e.de,
        tpearson@...torengineering.com, aik@....com, bgray@...ux.ibm.com,
        gregkh@...uxfoundation.org, sbhat@...ux.ibm.com,
        gbatra@...ux.vnet.ibm.com, vaibhav@...ux.ibm.com
Subject: [PATCH 1/2] powerpc: iommu: Bring back table group
 release_ownership() call

The commit 2ad56efa80db ("powerpc/iommu: Setup a default domain and
remove set_platform_dma_ops") refactored the code removing the
set_platform_dma_ops(). It missed out the table group
release_ownership() call which would have got called otherwise
during the guest shutdown via vfio_group_detach_container(). On
PPC64, this particular call actually sets up the 32-bit TCE table,
and enables the 64-bit DMA bypass etc. Now after guest shutdown,
the subsequent host driver (e.g megaraid-sas) probe post unbind
from vfio-pci fails like,

megaraid_sas 0031:01:00.0: Warning: IOMMU dma not supported: mask 0x7fffffffffffffff, table unavailable
megaraid_sas 0031:01:00.0: Warning: IOMMU dma not supported: mask 0xffffffff, table unavailable
megaraid_sas 0031:01:00.0: Failed to set DMA mask
megaraid_sas 0031:01:00.0: Failed from megasas_init_fw 6539

The patch brings back the call to table_group release_ownership()
call when switching back to PLATFORM domain.

Fixes: 2ad56efa80db ("powerpc/iommu: Setup a default domain and remove set_platform_dma_ops")
Signed-off-by: Shivaprasad G Bhat <sbhat@...ux.ibm.com>
---
 arch/powerpc/kernel/iommu.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index ebe259bdd462..ac7df43fa7ef 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1296,9 +1296,19 @@ spapr_tce_platform_iommu_attach_dev(struct iommu_domain *platform_domain,
 	if (!grp)
 		return -ENODEV;
 
-	table_group = iommu_group_get_iommudata(grp);
-	ret = table_group->ops->take_ownership(table_group);
-	iommu_group_put(grp);
+	if (platform_domain->type == IOMMU_DOMAIN_PLATFORM) {
+		ret = 0;
+		table_group = iommu_group_get_iommudata(grp);
+		/*
+		 * The domain being set to PLATFORM from earlier
+		 * BLOCKED. The table_group ownership has to be released.
+		 */
+		table_group->ops->release_ownership(table_group);
+	} else if (platform_domain->type == IOMMU_DOMAIN_BLOCKED) {
+		table_group = iommu_group_get_iommudata(grp);
+		ret = table_group->ops->take_ownership(table_group);
+		iommu_group_put(grp);
+	}
 
 	return ret;
 }