[Xen-devel] [PATCH RFC] pvh: set need_iommu early

[Elena Ufimtseva <elena.ufimtseva@xxxxxxxxxx>]

need_iommu has to be set earler for dom0 pvh specific init
functions. If not enabled, mmio regions are not mapped with iommu
during domain construction.

This was discovered when working on booting problems of pvh dom0
on two different machines (ThinkCentre M and Dell 5600T).
On ThinkCentre during pvh dom0 booting process, IOMMU would report
Page fault with EPT not present. The memory address of the page fault 
suggested that is mmio region for USB host controllers. The faulting 
address marked as Reserved in e820 map and is not part of any rmrr 
region reported by ACPI. 
These USB Host controllers have debugging devices which do behave 
strangely and obviously use these mmio addresses for IO.
In pv dom0 case, all mmio regions are mappped with IOMMUF_readable and
IOMMUF_writable flags.

The other part of equation for mmio pvh region mappings is that these are
typed with p2m_mmio_direct.  When requesting iommu flags based on memory
type in ept_set_entry, it returns 0 and the EPT are not being mapped with
iommu. To have correct mapping set, p2m_mmio_direct has to map to
IOMMUF_readable and IOMMUF_writable. This RFC patch is to follow.

Problem discussed in thread http://lists.xenproject.org/archives/html/xen-devel
/2014-12/msg01956.html was also solved by this change and correct memory type
to iommu flags setting.

I would like to ask for comments and opinions as there maybe a better way to
make these changes.

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@xxxxxxxxxx>
---
 xen/arch/x86/domain_build.c     | 4 +++-
 xen/drivers/passthrough/iommu.c | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
index 7993b17..cf8e776 100644
--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -1500,7 +1500,9 @@ int __init construct_dom0(
 
     if ( is_pvh_domain(d) )
     {
-        /* finally, fixup the page table, replacing mfns with pfns */
+       d->need_iommu = 1;
+
+       /* finally, fixup the page table, replacing mfns with pfns */
         pvh_fixup_page_tables_for_hap(v, v_start, v_end);
 
         /* the pt has correct pfn for si, now update the mfn in the p2m */
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index cc12735..d7012cb 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -154,7 +154,7 @@ void __hwdom_init iommu_hwdom_init(struct domain *d)
         return;
 
     register_keyhandler('o', &iommu_p2m_table);
-    d->need_iommu = !!iommu_dom0_strict;
+    d->need_iommu |= !!iommu_dom0_strict;
     if ( need_iommu(d) && !iommu_use_hap_pt(d) )
     {
         struct page_info *page;
-- 
2.1.3


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