[Xen-devel] [PATCH] linux/i386-PAE: avoid temporarily inconsistent pte-s

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

One more of these issues (which were considered fixed): Other than on
x86-64, i386 allows set_fixmap() to replace already present mappings.
Consequently, on PAE, care must be taken to not update the high half
of a pte while the low half is still holding the old value.

As always, tested on 2.6.22 and made apply on 2.6.18.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: head-2007-09-03/arch/i386/mm/pgtable-xen.c
===================================================================
--- head-2007-09-03.orig/arch/i386/mm/pgtable-xen.c     2007-06-01 
16:57:12.000000000 +0200
+++ head-2007-09-03/arch/i386/mm/pgtable-xen.c  2007-09-19 11:04:16.000000000 
+0200
@@ -77,87 +77,6 @@ void show_mem(void)
 }
 
 /*
- * Associate a virtual page frame with a given physical page frame 
- * and protection flags for that frame.
- */ 
-static void set_pte_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
-{
-       pgd_t *pgd;
-       pud_t *pud;
-       pmd_t *pmd;
-       pte_t *pte;
-
-       pgd = swapper_pg_dir + pgd_index(vaddr);
-       if (pgd_none(*pgd)) {
-               BUG();
-               return;
-       }
-       pud = pud_offset(pgd, vaddr);
-       if (pud_none(*pud)) {
-               BUG();
-               return;
-       }
-       pmd = pmd_offset(pud, vaddr);
-       if (pmd_none(*pmd)) {
-               BUG();
-               return;
-       }
-       pte = pte_offset_kernel(pmd, vaddr);
-       if (pgprot_val(flags))
-               /* <pfn,flags> stored as-is, to permit clearing entries */
-               set_pte(pte, pfn_pte(pfn, flags));
-       else
-               pte_clear(&init_mm, vaddr, pte);
-
-       /*
-        * It's enough to flush this one mapping.
-        * (PGE mappings get flushed as well)
-        */
-       __flush_tlb_one(vaddr);
-}
-
-/*
- * Associate a virtual page frame with a given physical page frame 
- * and protection flags for that frame.
- */ 
-static void set_pte_pfn_ma(unsigned long vaddr, unsigned long pfn,
-                          pgprot_t flags)
-{
-       pgd_t *pgd;
-       pud_t *pud;
-       pmd_t *pmd;
-       pte_t *pte;
-
-       pgd = swapper_pg_dir + pgd_index(vaddr);
-       if (pgd_none(*pgd)) {
-               BUG();
-               return;
-       }
-       pud = pud_offset(pgd, vaddr);
-       if (pud_none(*pud)) {
-               BUG();
-               return;
-       }
-       pmd = pmd_offset(pud, vaddr);
-       if (pmd_none(*pmd)) {
-               BUG();
-               return;
-       }
-       pte = pte_offset_kernel(pmd, vaddr);
-       if (pgprot_val(flags))
-               /* <pfn,flags> stored as-is, to permit clearing entries */
-               set_pte(pte, pfn_pte_ma(pfn, flags));
-       else
-               pte_clear(&init_mm, vaddr, pte);
-
-       /*
-        * It's enough to flush this one mapping.
-        * (PGE mappings get flushed as well)
-        */
-       __flush_tlb_one(vaddr);
-}
-
-/*
  * Associate a large virtual page frame with a given physical page frame 
  * and protection flags for that frame. pfn is for the base of the page,
  * vaddr is what the page gets mapped to - both must be properly aligned. 
@@ -200,6 +119,7 @@ EXPORT_SYMBOL(__FIXADDR_TOP);
 void __set_fixmap (enum fixed_addresses idx, maddr_t phys, pgprot_t flags)
 {
        unsigned long address = __fix_to_virt(idx);
+       pte_t pte;
 
        if (idx >= __end_of_fixed_addresses) {
                BUG();
@@ -207,16 +127,16 @@ void __set_fixmap (enum fixed_addresses 
        }
        switch (idx) {
        case FIX_WP_TEST:
-#ifdef CONFIG_X86_F00F_BUG
-       case FIX_F00F_IDT:
-#endif
        case FIX_VDSO:
-               set_pte_pfn(address, phys >> PAGE_SHIFT, flags);
+               pte = pfn_pte(phys >> PAGE_SHIFT, flags);
                break;
        default:
-               set_pte_pfn_ma(address, phys >> PAGE_SHIFT, flags);
+               pte = pfn_pte_ma(phys >> PAGE_SHIFT, flags);
                break;
        }
+       if (HYPERVISOR_update_va_mapping(address, pte,
+                                        UVMF_INVLPG|UVMF_ALL))
+               BUG();
        nr_fixmaps++;
 }
 




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