minios: don't rely on specific page table allocation scheme

Today mini-os is making assumptions how the page tables it is started
with are being allocated. Especially it is using the number of page
table frames to calculate which is the first unmapped pfn.

Instead of relying on page table number assumptions just look into the
page tables to find the first pfn not already mapped.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/arch/x86/mm.c b/arch/x86/mm.c
index 186659dfd4793c2ef6df73f22a0dc19395c72954..51aa96624473cf11e1f7e9c56e07c7f53ed66860 100644 (file)
--- a/arch/x86/mm.c
+++ b/arch/x86/mm.c
@@ -131,61 +131,6 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
     *pt_pfn += 1;
 }
 
-/*
- * Checks if a pagetable frame is needed at 'level' to map a given
- * address. Note, this function is specific to the initial page table
- * building.
- */
-static int need_pt_frame(unsigned long va, int level)
-{
-    unsigned long hyp_virt_start = HYPERVISOR_VIRT_START;
-#if defined(__x86_64__)
-    unsigned long hyp_virt_end = HYPERVISOR_VIRT_END;
-#else
-    unsigned long hyp_virt_end = 0xffffffff;
-#endif
-
-    /* In general frames will _not_ be needed if they were already
-       allocated to map the hypervisor into our VA space */
-#if defined(__x86_64__)
-    if ( level == L3_FRAME )
-    {
-        if ( l4_table_offset(va) >= 
-             l4_table_offset(hyp_virt_start) &&
-             l4_table_offset(va) <= 
-             l4_table_offset(hyp_virt_end))
-            return 0;
-        return 1;
-    } 
-    else
-#endif
-
-    if ( level == L2_FRAME )
-    {
-#if defined(__x86_64__)
-        if ( l4_table_offset(va) >= 
-             l4_table_offset(hyp_virt_start) &&
-             l4_table_offset(va) <= 
-             l4_table_offset(hyp_virt_end))
-#endif
-            if ( l3_table_offset(va) >= 
-                 l3_table_offset(hyp_virt_start) &&
-                 l3_table_offset(va) <= 
-                 l3_table_offset(hyp_virt_end))
-                return 0;
-
-        return 1;
-    } 
-    else 
-        /* Always need l1 frames */
-        if ( level == L1_FRAME )
-            return 1;
-
-    printk("ERROR: Unknown frame level %d, hypervisor %lx,%lx\n", 
-           level, hyp_virt_start, hyp_virt_end);
-    return -1;
-}
-
 /*
  * Build the initial pagetable.
  */
@@ -200,8 +145,9 @@ static void build_pagetable(unsigned long *start_pfn, unsigned long *max_pfn)
     int count = 0;
     int rc;
 
-    pfn_to_map = 
-        (start_info.nr_pt_frames - NOT_L1_FRAMES) * L1_PAGETABLE_ENTRIES;
+    /* Be conservative: even if we know there will be more pages already
+       mapped, start the loop at the very beginning. */
+    pfn_to_map = *start_pfn;
 
     if ( *max_pfn >= virt_to_pfn(HYPERVISOR_VIRT_START) )
     {
@@ -229,9 +175,8 @@ static void build_pagetable(unsigned long *start_pfn, unsigned long *max_pfn)
 #if defined(__x86_64__)
         offset = l4_table_offset(start_address);
         /* Need new L3 pt frame */
-        if ( !(start_address & L3_MASK) )
-            if ( need_pt_frame(start_address, L3_FRAME) ) 
-                new_pt_frame(&pt_pfn, pt_mfn, offset, L3_FRAME);
+        if ( !(tab[offset] & _PAGE_PRESENT) )
+            new_pt_frame(&pt_pfn, pt_mfn, offset, L3_FRAME);
 
         page = tab[offset];
         pt_mfn = pte_to_mfn(page);
@@ -239,29 +184,33 @@ static void build_pagetable(unsigned long *start_pfn, unsigned long *max_pfn)
 #endif
         offset = l3_table_offset(start_address);
         /* Need new L2 pt frame */
-        if ( !(start_address & L2_MASK) )
-            if ( need_pt_frame(start_address, L2_FRAME) )
-                new_pt_frame(&pt_pfn, pt_mfn, offset, L2_FRAME);
+        if ( !(tab[offset] & _PAGE_PRESENT) )
+            new_pt_frame(&pt_pfn, pt_mfn, offset, L2_FRAME);
 
         page = tab[offset];
         pt_mfn = pte_to_mfn(page);
         tab = to_virt(mfn_to_pfn(pt_mfn) << PAGE_SHIFT);
         offset = l2_table_offset(start_address);        
         /* Need new L1 pt frame */
-        if ( !(start_address & L1_MASK) )
-            if ( need_pt_frame(start_address, L1_FRAME) )
-                new_pt_frame(&pt_pfn, pt_mfn, offset, L1_FRAME);
+        if ( !(tab[offset] & _PAGE_PRESENT) )
+            new_pt_frame(&pt_pfn, pt_mfn, offset, L1_FRAME);
 
         page = tab[offset];
         pt_mfn = pte_to_mfn(page);
+        tab = to_virt(mfn_to_pfn(pt_mfn) << PAGE_SHIFT);
         offset = l1_table_offset(start_address);
 
-        mmu_updates[count].ptr =
-            ((pgentry_t)pt_mfn << PAGE_SHIFT) + sizeof(pgentry_t) * offset;
-        mmu_updates[count].val = 
-            (pgentry_t)pfn_to_mfn(pfn_to_map++) << PAGE_SHIFT | L1_PROT;
-        count++;
-        if ( count == L1_PAGETABLE_ENTRIES || pfn_to_map == *max_pfn )
+        if ( !(tab[offset] & _PAGE_PRESENT) )
+        {
+            mmu_updates[count].ptr =
+                ((pgentry_t)pt_mfn << PAGE_SHIFT) + sizeof(pgentry_t) * offset;
+            mmu_updates[count].val =
+                (pgentry_t)pfn_to_mfn(pfn_to_map) << PAGE_SHIFT | L1_PROT;
+            count++;
+        }
+        pfn_to_map++;
+        if ( count == L1_PAGETABLE_ENTRIES ||
+             (count && pfn_to_map == *max_pfn) )
         {
             rc = HYPERVISOR_mmu_update(mmu_updates, count, NULL, DOMID_SELF);
             if ( rc < 0 )

diff --git a/include/x86/arch_mm.h b/include/x86/arch_mm.h
index 23cfca7bfe190296030a3276c32064b5453b7762..58f29fcfaad80c47e1a1515662a19ea2042491b3 100644 (file)
--- a/include/x86/arch_mm.h
+++ b/include/x86/arch_mm.h
@@ -56,12 +56,6 @@
 
 #define L2_MASK  ((1UL << L3_PAGETABLE_SHIFT) - 1)
 
-/*
- * If starting from virtual address greater than 0xc0000000,
- * this value will be 2 to account for final mid-level page
- * directory which is always mapped in at this location.
- */
-#define NOT_L1_FRAMES           3
 #define PRIpte "016llx"
 #ifndef __ASSEMBLY__
 typedef uint64_t pgentry_t;
@@ -87,7 +81,6 @@ typedef uint64_t pgentry_t;
 #define L2_MASK  ((1UL << L3_PAGETABLE_SHIFT) - 1)
 #define L3_MASK  ((1UL << L4_PAGETABLE_SHIFT) - 1)
 
-#define NOT_L1_FRAMES           3
 #define PRIpte "016lx"
 #ifndef __ASSEMBLY__
 typedef unsigned long pgentry_t;