hw/i386/amd_iommu: Fix device setup failure when PT is on.

Commit c1f46999ef506 ("amd_iommu: Add support for pass though mode")
introduces the support for "pt" flag by enabling nodma memory when
"pt=off". This allowed VFIO devices to successfully register notifiers
by using nodma region.

But, This also broke things when guest is booted with the iommu=nopt
because, devices bypass the IOMMU and use untranslated addresses (IOVA) to
perform DMA reads/writes to the nodma memory region, ultimately resulting in
a failure to setup the devices in the guest.

Fix the above issue by always enabling the amdvi_dev_as->iommu memory region.
But this will once again cause VFIO devices to fail while registering the
notifiers with AMD IOMMU memory region.

Fixes: c1f46999ef506 ("amd_iommu: Add support for pass though mode")
Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Message-Id: <20250516100535.4980-2-sarunkod@amd.com>
Fixes: c1f46999ef506 ("amd_iommu: Add support for pass though mode")
Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>

1 files changed, 2 insertions, 10 deletions

diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
index 0775c8f..17379db 100644
--- a/hw/i386/amd_iommu.c
+++ b/hw/i386/amd_iommu.c
@@ -1426,7 +1426,6 @@ static AddressSpace *amdvi_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
     AMDVIState *s = opaque;
     AMDVIAddressSpace **iommu_as, *amdvi_dev_as;
     int bus_num = pci_bus_num(bus);
-    X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(s);
 
     iommu_as = s->address_spaces[bus_num];
 
@@ -1486,15 +1485,8 @@ static AddressSpace *amdvi_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
                                             AMDVI_INT_ADDR_FIRST,
                                             &amdvi_dev_as->iommu_ir, 1);
 
-        if (!x86_iommu->pt_supported) {
-            memory_region_set_enabled(&amdvi_dev_as->iommu_nodma, false);
-            memory_region_set_enabled(MEMORY_REGION(&amdvi_dev_as->iommu),
-                                      true);
-        } else {
-            memory_region_set_enabled(MEMORY_REGION(&amdvi_dev_as->iommu),
-                                      false);
-            memory_region_set_enabled(&amdvi_dev_as->iommu_nodma, true);
-        }
+        memory_region_set_enabled(&amdvi_dev_as->iommu_nodma, false);
+        memory_region_set_enabled(MEMORY_REGION(&amdvi_dev_as->iommu), true);
     }
     return &iommu_as[devfn]->as;
 }