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[Xen-devel] [PATCH for-4.12 v3 1/8] dom0/pvh: align allocation and mapping order to start address

The p2m and iommu mapping code always had the requirement that
addresses and orders must be aligned when populating the p2m or the
iommu page tables.

PVH dom0 builder didn't take this requirement into account, and can
call into the p2m/iommu mapping helpers with addresses and orders that
are not aligned.

Fix this by making sure the orders passed to the physmap population
helpers are always aligned to the guest address to be populated.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Without this patch trying to create a PVH dom0 will trigger an assert
on certain hardware depending on the memory map.
Changes since v1:
 - Reword commit message.
 xen/arch/x86/hvm/dom0_build.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index 51cf490811..a571d15c13 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -152,6 +152,8 @@ static int __init pvh_populate_memory_range(struct domain 
         order = get_order_from_pages(end - start + 1);
         order = min(order ? order - 1 : 0, max_order);
+        /* The order allocated and populated must be aligned to the address. */
+        order = min(order, start ? find_first_set_bit(start) : MAX_ORDER);
         page = alloc_domheap_pages(d, order, dom0_memflags | MEMF_no_scrub);
         if ( page == NULL )
2.17.2 (Apple Git-113)

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