Messages in this thread Patch in this message | | | From | Jeremy Fitzhardinge <> | Subject | [PATCH 16/16] xen/i386: make sure initial VGA/ISA mappings are not overridden | Date | Wed, 27 May 2009 00:15:38 -0700 |
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From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
arch/x86/mm/init_32.c overrides the ISA/VGA mappings with direct mappings which do not have _PAGE_IOMAP set, thereby making the ISA space inaccessible.
This patch adds to the existing hack to make sure the pre-constructed ISA mappings are not incorrectly overwritten.
Thanks to Gerd Hoffman for pointing this out.
[ Impact: Makes 32-bit dom0 VGA work properly. ]
Diagnosed-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- arch/x86/xen/mmu.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 85d9d18..331e52d 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1502,10 +1502,17 @@ static void *xen_kmap_atomic_pte(struct page *page, enum km_type type) #ifdef CONFIG_X86_32 static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte) { - /* If there's an existing pte, then don't allow _PAGE_RW to be set */ - if (pte_val_ma(*ptep) & _PAGE_PRESENT) + pte_t oldpte = *ptep; + + if (pte_flags(oldpte) & _PAGE_PRESENT) { + /* Don't allow existing IO mappings to be overridden */ + if (pte_flags(oldpte) & _PAGE_IOMAP) + pte = oldpte; + + /* Don't allow _PAGE_RW to be set on existing pte */ pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) & pte_val_ma(pte)); + } return pte; } -- 1.6.0.6
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