[Xen-devel] [PATCH for-4.12 v2 2/7] amd/npt/shadow: replace assert that prevents creating 2M/1G 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.

Replace the assert to allow 2M/1G entries to be created for MMIO
regions and add some extra asserts as a replacement to make sure
there's no overlapping with MMIO read-only ranges.

Note that 1G MMIO entries will not be created unless mmio_order is
changed to allow it.

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.
---
Changes since v1:
 - Fix subject.
 - Replace the assert with a suitable one.
---
 xen/arch/x86/mm/p2m-pt.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 12f92cf1f0..791600f6ba 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -576,7 +576,15 @@ 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);
+        if ( p2mt == p2m_mmio_direct )
+            ASSERT(!mfn_eq(mfn, INVALID_MFN) &&
+                   !rangeset_overlaps_range(mmio_ro_ranges, mfn_x(mfn),
+                                            mfn_x(mfn) + PFN_DOWN(MB(2))));
+        else if ( p2m_allows_invalid_mfn(p2mt) || p2mt == p2m_invalid ||
+                  p2mt == p2m_mmio_dm )
+            ASSERT(mfn_valid(mfn) || mfn_eq(mfn, INVALID_MFN));
+        else
+            ASSERT(mfn_valid(mfn));
         l3e_content = mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt)
             ? p2m_l3e_from_pfn(mfn_x(mfn),
                                p2m_type_to_flags(p2m, p2mt, mfn, 2))
@@ -668,7 +676,15 @@ 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);
+        if ( p2mt == p2m_mmio_direct )
+            ASSERT(!mfn_eq(mfn, INVALID_MFN) &&
+                   !rangeset_overlaps_range(mmio_ro_ranges, mfn_x(mfn),
+                                            mfn_x(mfn) + PFN_DOWN(MB(2))));
+        else if ( p2m_allows_invalid_mfn(p2mt) || p2mt == p2m_invalid ||
+                  p2mt == p2m_mmio_dm )
+            ASSERT(mfn_valid(mfn) || mfn_eq(mfn, INVALID_MFN));
+        else
+            ASSERT(mfn_valid(mfn));
         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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