[Xen-devel] [PATCH for-4.12 2/8] amd/ntp: remove assert that prevents creating 2M MMIO entries

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

The assert was originally added to make sure that higher order
regions (> PAGE_ORDER_4K) could not be used to bypass the
mmio_ro_ranges check performed by p2m_type_to_flags.

This however is already checked in set_mmio_p2m_entry, which makes
sure that higher order mappings don't overlap with mmio_ro_ranges,
thus allowing the creation of high order MMIO mappings safely.

Remove the assert to allow 2M entries to be created for MMIO regions
that don't overlap with mmio_ro_ranges.

Suggested-by: George Dunlap <george.dunlap@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
---
Without this patch trying to create a PVH dom0 will trigger an assert
on certain hardware depending on the memory map.
---
 xen/arch/x86/mm/p2m-pt.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 12f92cf1f0..b8996e5415 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -668,7 +668,6 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t 
mfn,
         }
 
         ASSERT(p2m_flags_to_type(flags) != p2m_ioreq_server);
-        ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
         l2e_content = mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt)
             ? p2m_l2e_from_pfn(mfn_x(mfn),
                                p2m_type_to_flags(p2m, p2mt, mfn, 1))
-- 
2.20.1


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