[Xen-devel] [patch] pin/unpin must flush tlb

[Gerd Knorr <kraxel@xxxxxxx>]

  Hi,

Patch below is needed to make my system work stable in PAE mode.
Havn't seen problems without PAE, not sure whenever thats just
pure luck or whenever there is a bug in my PAE xenlinux kernel.
To me it looks like a generic bug though.

I've actually trapped into problems with unpin only:  A process
exits, somewhere in exit_mm() the page tables are unpinned,
shortly thereafter the mappings are cleared.  While doing so the
kernel oopses in zap_pte_range(), on page table write access.
Probably due to some stale tlb entry where the page is still
tagged read-only.

cheers,
  Gerd

Index: linux-2.6.11/arch/xen/i386/mm/pgtable.c
===================================================================
--- linux-2.6.11.orig/arch/xen/i386/mm/pgtable.c        2005-06-22 
16:25:17.000000000 +0200
+++ linux-2.6.11/arch/xen/i386/mm/pgtable.c     2005-06-23 18:20:45.000000000 
+0200
@@ -486,7 +486,8 @@ void mm_pin(struct mm_struct *mm)
     mm_walk(mm, PAGE_KERNEL_RO);
     HYPERVISOR_update_va_mapping(
         (unsigned long)mm->pgd,
-        pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL_RO), 0);
+        pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL_RO),
+       UVMF_TLB_FLUSH);
     xen_pgd_pin(__pa(mm->pgd));
     mm->context.pinned = 1;
     spin_lock(&mm_unpinned_lock);
@@ -505,6 +506,7 @@ void mm_unpin(struct mm_struct *mm)
         (unsigned long)mm->pgd,
         pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL), 0);
     mm_walk(mm, PAGE_KERNEL);
+    xen_tlb_flush();
     mm->context.pinned = 0;
     spin_lock(&mm_unpinned_lock);
     list_add(&mm->context.unpinned, &mm_unpinned);

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