[Xen-devel] [PATCH] x86/NPT: deal with fallout from 2Mb/1Gb unmapping change

["Jan Beulich" <JBeulich@xxxxxxxx>]

Commit efa9596e9d ("x86/mm: fix incorrect unmapping of 2MB and 1GB
pages") left the NPT code untouched, as there is no explicit alignment
check matching the one in EPT code. However, the now more widespread
storing of INVALID_MFN into PTEs requires adjustments:
- calculations when shattering large pages may spill into the p2m type
  field (converting p2m_populate_on_demand to p2m_grant_map_rw) - use
  OR instead of PLUS,
- the use of plain l{2,3}e_from_pfn() in p2m_pt_set_entry() results in
  all upper (flag) bits being clobbered - introduce and use
  p2m_l{2,3}e_from_pfn(), paralleling the existing L1 variant.

Reported-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -45,13 +45,20 @@
 #undef page_to_mfn
 #define page_to_mfn(_pg) _mfn(__page_to_mfn(_pg))
 
-/* We may store INVALID_MFN in l1 PTEs. We need to clip this
- * to avoid trampling over higher-order bits (NX, p2m type, IOMMU flags).  We
- * seem to not need to unclip on the return path, as callers are concerned only
- * with p2m type in such cases. 
+/*
+ * We may store INVALID_MFN in PTEs.  We need to clip this to avoid trampling
+ * over higher-order bits (NX, p2m type, IOMMU flags).  We seem to not need
+ * to unclip on the read path, as callers are concerned only with p2m type in
+ * such cases.
  */
 #define p2m_l1e_from_pfn(pfn, flags)    \
     l1e_from_pfn((pfn) & (PADDR_MASK >> PAGE_SHIFT), (flags))
+#define p2m_l2e_from_pfn(pfn, flags)    \
+    l2e_from_pfn((pfn) & ((PADDR_MASK & ~(_PAGE_PSE_PAT | 0UL)) \
+                          >> PAGE_SHIFT), (flags) | _PAGE_PSE)
+#define p2m_l3e_from_pfn(pfn, flags)    \
+    l3e_from_pfn((pfn) & ((PADDR_MASK & ~(_PAGE_PSE_PAT | 0UL)) \
+                          >> PAGE_SHIFT), (flags) | _PAGE_PSE)
 
 /* PTE flags for the various types of p2m entry */
 #define P2M_BASE_FLAGS \
@@ -243,7 +250,7 @@ p2m_next_level(struct p2m_domain *p2m, v
         l1_entry = __map_domain_page(pg);
         for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
         {
-            new_entry = l1e_from_pfn(pfn + (i * L1_PAGETABLE_ENTRIES), flags);
+            new_entry = l1e_from_pfn(pfn | (i * L1_PAGETABLE_ENTRIES), flags);
             p2m_add_iommu_flags(&new_entry, 1, 
IOMMUF_readable|IOMMUF_writable);
             p2m->write_p2m_entry(p2m, gfn, l1_entry + i, new_entry, 2);
         }
@@ -277,7 +284,7 @@ p2m_next_level(struct p2m_domain *p2m, v
         l1_entry = __map_domain_page(pg);
         for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
         {
-            new_entry = l1e_from_pfn(pfn + i, flags);
+            new_entry = l1e_from_pfn(pfn | i, flags);
             p2m_add_iommu_flags(&new_entry, 0, 0);
             p2m->write_p2m_entry(p2m, gfn, l1_entry + i, new_entry, 1);
         }
@@ -595,8 +602,8 @@ p2m_pt_set_entry(struct p2m_domain *p2m,
         ASSERT(p2m_flags_to_type(flags) != p2m_ioreq_server);
         ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
         l3e_content = mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt)
-            ? l3e_from_pfn(mfn_x(mfn),
-                           p2m_type_to_flags(p2m, p2mt, mfn, 2) | _PAGE_PSE)
+            ? p2m_l3e_from_pfn(mfn_x(mfn),
+                               p2m_type_to_flags(p2m, p2mt, mfn, 2))
             : l3e_empty();
         entry_content.l1 = l3e_content.l3;
 
@@ -686,13 +693,10 @@ p2m_pt_set_entry(struct p2m_domain *p2m,
 
         ASSERT(p2m_flags_to_type(flags) != p2m_ioreq_server);
         ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
-        if ( mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt) )
-            l2e_content = l2e_from_pfn(mfn_x(mfn),
-                                       p2m_type_to_flags(p2m, p2mt, mfn, 1) |
-                                       _PAGE_PSE);
-        else
-            l2e_content = l2e_empty();
-        
+        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))
+            : l2e_empty();
         entry_content.l1 = l2e_content.l2;
 
         if ( entry_content.l1 != 0 )

Attachment: x86-p2m-pt-INVALID_MFN.patch
Description: Text document

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