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

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Commit c1f46999ef ("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: c1f46999ef ("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: c1f46999ef ("amd_iommu: Add support for pass though mode")
Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
This commit is contained in:
Sairaj Kodilkar 2025-05-16 15:35:34 +05:30 • committed by Michael S. Tsirkin
parent ac8fc4ccac
commit 31753d5a33
1 changed files with 2 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

12
hw/i386/amd_iommu.c
View file

@ -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;
}