[Xen-changelog] [xen-unstable] [LINUX] Fix clear_fixmap().

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Node ID c6efd6c2feaa3ec851685cc872a1ce989d998220
# Parent  16977bd93dbebe30060e4b4462938f21f5b14275
[LINUX] Fix clear_fixmap().

On i386-PAE, clear_fixmap() results in ill use of set_pte(). In all
contexts, p2m translations shouldn't occur here. Note that this is not
really an issue on native linux, as there is
(a) no pfn-to-mfn translation and
(b) __set_fixmap() takes an unsigned long physical address rather than
    a paddr_t, which makes it so that bits 32 and up of the physical
    address are always zero, permitting either order store when
    clearing the entry.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---
 linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c |   14 ++++++++++----
 linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c  |    5 ++++-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff -r 16977bd93dbe -r c6efd6c2feaa 
linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
--- a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c   Mon Nov 13 12:06:21 
2006 +0000
+++ b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c   Mon Nov 13 13:37:54 
2006 +0000
@@ -102,8 +102,11 @@ static void set_pte_pfn(unsigned long va
                return;
        }
        pte = pte_offset_kernel(pmd, vaddr);
-       /* <pfn,flags> stored as-is, to permit clearing entries */
-       set_pte(pte, pfn_pte(pfn, flags));
+       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.
@@ -140,8 +143,11 @@ static void set_pte_pfn_ma(unsigned long
                return;
        }
        pte = pte_offset_kernel(pmd, vaddr);
-       /* <pfn,flags> stored as-is, to permit clearing entries */
-       set_pte(pte, pfn_pte_ma(pfn, flags));
+       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.
diff -r 16977bd93dbe -r c6efd6c2feaa 
linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c
--- a/linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c    Mon Nov 13 12:06:21 
2006 +0000
+++ b/linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c    Mon Nov 13 13:37:54 
2006 +0000
@@ -260,7 +260,10 @@ static void set_pte_phys(unsigned long v
                        return;
                }
        }
-       new_pte = pfn_pte(phys >> PAGE_SHIFT, prot);
+       if (pgprot_val(prot))
+               new_pte = pfn_pte(phys >> PAGE_SHIFT, prot);
+       else
+               new_pte = __pte(0);
 
        pte = pte_offset_kernel(pmd, vaddr);
        if (!pte_none(*pte) &&

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