[xen stable-4.18] iommu/amd-vi: do not error if device referenced in IVMD is not behind any IOMMU

[patchbot@xxxxxxx]

commit b9bf85b5fd9106f4d9e27867ffd1d02bb3ff264b
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Tue Oct 29 16:41:42 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Oct 29 16:41:42 2024 +0100

    iommu/amd-vi: do not error if device referenced in IVMD is not behind any 
IOMMU
    
    IVMD table contains restrictions about memory which must be mandatory 
assigned
    to devices (and which permissions it should use), or memory that should be
    never accessible to devices.
    
    Some hardware however contains ranges in IVMD that reference devices 
outside of
    the IVHD tables (in other words, devices not behind any IOMMU).  Such 
mismatch
    will cause Xen to fail in register_range_for_device(), ultimately leading to
    the IOMMU being disabled, and Xen crashing as x2APIC support might be 
already
    enabled and relying on the IOMMU functionality.
    
    Relax IVMD parsing: allow IVMD blocks to reference devices not assigned to 
any
    IOMMU.  It's impossible for Xen to fulfill the requirement in the IVMD 
block if
    the device is not behind any IOMMU, but it's no worse than booting without
    IOMMU support, and thus not parsing ACPI IVRS in the first place.
    
    Reported-by: Willi Junga <xenproject@xxxxxx>
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 2defb544900a11f93104ac68d2f8beba89d4bd02
    master date: 2024-10-15 14:23:59 +0200
---
 xen/drivers/passthrough/amd/iommu_acpi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/passthrough/amd/iommu_acpi.c 
b/xen/drivers/passthrough/amd/iommu_acpi.c
index 96d8879e7b..59d30a4a2c 100644
--- a/xen/drivers/passthrough/amd/iommu_acpi.c
+++ b/xen/drivers/passthrough/amd/iommu_acpi.c
@@ -248,8 +248,9 @@ static int __init register_range_for_device(
     iommu = find_iommu_for_device(seg, bdf);
     if ( !iommu )
     {
-        AMD_IOMMU_ERROR("IVMD: no IOMMU for Dev_Id %#x\n", bdf);
-        return -ENODEV;
+        AMD_IOMMU_WARN("IVMD: no IOMMU for device %pp - ignoring constrain\n",
+                       &PCI_SBDF(seg, bdf));
+        return 0;
     }
     req = ivrs_mappings[bdf].dte_requestor_id;
 
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