[XEN PATCH v4 5/5] AMD-Vi: Disable intrerrupt remapping if cx16 is not supported

[Teddy Astie <teddy.astie@xxxxxxxxxx>]

All hardware with AMD-Vi has CMPXCHG16 support.  Check this at initialisation
time, and remove the effectively-dead logic for the non-cx16 case.

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
 xen/drivers/passthrough/amd/iommu_intr.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/drivers/passthrough/amd/iommu_intr.c 
b/xen/drivers/passthrough/amd/iommu_intr.c
index 7fc796dec2..9ab7c68749 100644
--- a/xen/drivers/passthrough/amd/iommu_intr.c
+++ b/xen/drivers/passthrough/amd/iommu_intr.c
@@ -649,6 +649,12 @@ bool __init cf_check iov_supports_xt(void)
     if ( !iommu_enable || !iommu_intremap )
         return false;
 
+    if ( unlikely(!cpu_has_cx16) )
+    {
+        AMD_IOMMU_WARN("CPU doesn't support CMPXCHG16B, disable interrupt 
remapping\n");
+        return false;
+    }
+
     if ( amd_iommu_prepare(true) )
         return false;
 
-- 
2.44.0



Teddy Astie | Vates XCP-ng Intern

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