Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Jul 22, 2019 at 08:20:36AM +0000, Paul Durrant wrote:
> > -----Original Message-----
> [snip]
> > > (XEN) Domain heap initialised
> > > (XEN) ACPI: 32/64X FACS address mismatch in FADT -
> > > 8ce8ef80/0000000000000000, using 32
> > > (XEN) IOAPIC[0]: apic_id 2, version 32, address 0xfec00000, GSI 0-119
> > > (XEN) Enabling APIC mode:  Flat.  Using 1 I/O APICs
> > > (XEN) [VT-D]  RMRR address range 8d800000..8fffffff not in reserved
> > > memory; need "iommu_inclusive_mapping=1"?
> 
> This is your problem. In versions prior to 4.11 (I think, and certainly 4.12) 
> iommu_inclusive_mapping used to default on, whereas now it appears to default 
> off. In most circumstances this is fine because there is a new flag, 
> iommu_hwdom_reserved, which defaults on and this makes sure that all e820 
> reserved regions are identity mapped (which usually covers undeclared RMRRs). 
> You have the opposite problem... a declared RMRR which is not reserved, so 
> you will need iommu_inclusive_mapping.

I think there's a bug in the initialization of iommu for a PV dom0,
which leaves dom0 without rmrr entries. Can you try the patch below
and report whether it solves your issue?

Thanks, Roger.
---8<---
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 79ec6719f5..9d91f0d633 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -185,7 +185,7 @@ void __hwdom_init iommu_hwdom_init(struct domain *d)
     register_keyhandler('o', &iommu_dump_p2m_table, "dump iommu p2m table", 0);
 
     hd->status = IOMMU_STATUS_initializing;
-    hd->need_sync = iommu_hwdom_strict && !iommu_use_hap_pt(d);
+    hd->need_sync = !iommu_use_hap_pt(d);
     if ( need_iommu_pt_sync(d) )
     {
         struct page_info *page;


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