[xen master] x86/mm: avoid phys_to_nid() calls for invalid addresses

[patchbot@xxxxxxx]

commit 12b593ca0d61ef884c2f2de15ed36b4900fc92b2
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Dec 13 12:36:54 2022 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Dec 16 19:25:18 2022 +0000

    x86/mm: avoid phys_to_nid() calls for invalid addresses
    
    With phys_to_nid() now actively checking that a valid node ID is on
    record, the two uses in paging_init() can actually trigger at least the
    2nd of the assertions there. They're used to calculate allocation flags,
    but the calculated flags wouldn't be used when dealing with an invalid
    (unpopulated) address range. Defer the calculations such that they can
    be done with a validated MFN in hands. This also does away with the
    artificial calculations of an address to pass to phys_to_nid().
    
    Note that while the variable is provably written before use, at least
    some compiler versions can't actually verify that. Hence the variable
    also needs to gain a (dead) initializer.
    
    Fixes: e9c72d524fbd ("xen/x86: Use ASSERT instead of VIRTUAL_BUG_ON for 
phys_to_nid")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/x86_64/mm.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 3510a5affe..c9ddaaf36f 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -498,7 +498,7 @@ error:
 void __init paging_init(void)
 {
     unsigned long i, mpt_size, va;
-    unsigned int n, memflags;
+    unsigned int n, memflags = 0;
     l3_pgentry_t *l3_ro_mpt;
     l2_pgentry_t *pl2e = NULL, *l2_ro_mpt = NULL;
     struct page_info *l1_pg;
@@ -547,8 +547,6 @@ void __init paging_init(void)
     {
         BUILD_BUG_ON(RO_MPT_VIRT_START & ((1UL << L3_PAGETABLE_SHIFT) - 1));
         va = RO_MPT_VIRT_START + (i << L2_PAGETABLE_SHIFT);
-        memflags = MEMF_node(phys_to_nid(i <<
-            (L2_PAGETABLE_SHIFT - 3 + PAGE_SHIFT)));
 
         if ( cpu_has_page1gb &&
              !((unsigned long)pl2e & ~PAGE_MASK) &&
@@ -559,10 +557,15 @@ void __init paging_init(void)
             for ( holes = k = 0; k < 1 << PAGETABLE_ORDER; ++k)
             {
                 for ( n = 0; n < CNT; ++n)
-                    if ( mfn_valid(_mfn(MFN(i + k) + n * PDX_GROUP_COUNT)) )
+                {
+                    mfn = _mfn(MFN(i + k) + n * PDX_GROUP_COUNT);
+                    if ( mfn_valid(mfn) )
                         break;
+                }
                 if ( n == CNT )
                     ++holes;
+                else if ( k == holes )
+                    memflags = MEMF_node(phys_to_nid(mfn_to_maddr(mfn)));
             }
             if ( k == holes )
             {
@@ -593,8 +596,14 @@ void __init paging_init(void)
         }
 
         for ( n = 0; n < CNT; ++n)
-            if ( mfn_valid(_mfn(MFN(i) + n * PDX_GROUP_COUNT)) )
+        {
+            mfn = _mfn(MFN(i) + n * PDX_GROUP_COUNT);
+            if ( mfn_valid(mfn) )
+            {
+                memflags = MEMF_node(phys_to_nid(mfn_to_maddr(mfn)));
                 break;
+            }
+        }
         if ( n == CNT )
             l1_pg = NULL;
         else if ( (l1_pg = alloc_domheap_pages(NULL, PAGETABLE_ORDER,
@@ -663,15 +672,19 @@ void __init paging_init(void)
                  sizeof(*compat_machine_to_phys_mapping));
     for ( i = 0; i < (mpt_size >> L2_PAGETABLE_SHIFT); i++, pl2e++ )
     {
-        memflags = MEMF_node(phys_to_nid(i <<
-            (L2_PAGETABLE_SHIFT - 2 + PAGE_SHIFT)));
         for ( n = 0; n < CNT; ++n)
-            if ( mfn_valid(_mfn(MFN(i) + n * PDX_GROUP_COUNT)) )
+        {
+            mfn = _mfn(MFN(i) + n * PDX_GROUP_COUNT);
+            if ( mfn_valid(mfn) )
+            {
+                memflags = MEMF_node(phys_to_nid(mfn_to_maddr(mfn)));
                 break;
+            }
+        }
         if ( n == CNT )
             continue;
         if ( (l1_pg = alloc_domheap_pages(NULL, PAGETABLE_ORDER,
-                                               memflags)) == NULL )
+                                          memflags)) == NULL )
             goto nomem;
         map_pages_to_xen(
             RDWR_COMPAT_MPT_VIRT_START + (i << L2_PAGETABLE_SHIFT),
--
generated by git-patchbot for /home/xen/git/xen.git#master