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Re: [Xen-devel] [PATCH 1/2] AMD IOMMU: also spot missing IO-APIC entries in IVRS table



On 2/6/2013 9:52 AM, Jan Beulich wrote:
On 06.02.13 at 15:41, Boris Ostrovsky<boris.ostrovsky@xxxxxxxxxx>  wrote:
On 2/6/2013 8:12 AM, Jan Beulich wrote:


+    /* Each IO-APIC must have been mentioned in the table. */
+    for ( apic = 0; !error&&   apic<   nr_ioapics; ++apic )
+    {
+        if ( !nr_ioapic_entries[apic] ||
+             ioapic_sbdf[IO_APIC_ID(apic)].pin_setup )
+            continue;
+
+        printk(XENLOG_ERR "IVHD Error: no information for IO-APIC %#x\n",
+               IO_APIC_ID(apic));
+        if ( amd_iommu_perdev_intremap )
+            error = -ENXIO;
+        else
+        {
+            ioapic_sbdf[IO_APIC_ID(apic)].pin_setup = xzalloc_array(
+                unsigned long, BITS_TO_LONGS(nr_ioapic_entries[apic]));
+            if ( !ioapic_sbdf[IO_APIC_ID(apic)].pin_setup )
+            {
+                printk(XENLOG_ERR "IVHD Error: Out of memory\n");
+                error = -ENOMEM;
+            }
+        }
+    }
+
       return error;
   }


Don't we end up with ioapic_sbdf[IO_APIC_ID(apic)].bdf/seg being
uninitialized? They are usually set in parse_ivhd_device_special(), at
the same time pin_setup is allocated, but with IVRS broken in this way
we'll never get there, will we?

Correct. .bdf/.seg being uninitialized is no much of a problem
when using global intremap tables though.

Since this patch has been tested it clearly must have worked somehow but I don't understand where you'd get bdf and seg in amd_iommu_ioapic_update_ire() and then manage to find the right IOMMU.

-boris

> And certainly not on
a system with just a single IOMMU (as was the case on the
crashing system). Do you see alternatives? Disable the IOMMU
always, even if not using global remap tables? That could be
seen as a regression, as at least global remap tables worked fine
so far on such systems.






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