[Xen-devel] [PATCH] AMD/IOMMU: Process softirqs while building dom0 iommu mappings

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Recent changes which have made their way into xen-4.2 stable have pushed the
runtime of construct_dom0() over 5 seconds, which has caused regressions in
XenServer testing because of our 5 second watchdog.

The root cause is that amd_iommu_dom0_init() does not process softirqs and in
particular the nmi_timer which causes the watchdog to decide that no useful
progress is being made.

This patch adds periodic calls to process_pending_softirqs() at the same
interval as the Intel variant of this function.  The server which was failing
with the watchdog test now boots reliably with a timeout of 1 second.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

---
This patch should be backported to Xen-4.2 and 4.1

diff -r a6b81234b189 -r 418b06908cc0 xen/drivers/passthrough/amd/pci_amd_iommu.c
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -317,6 +317,9 @@ static void __init amd_iommu_dom0_init(s
             if ( mfn_valid(pfn) )
                 amd_iommu_map_page(d, pfn, pfn, 
                                    IOMMUF_readable|IOMMUF_writable);
+
+            if ( !(i & 0xfffff) )
+                process_pending_softirqs();
         }
     }
 

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