[Xen-devel] [PATCH 8/8] xen/mmu: Set _PAGE_IOMAP if PFN is in identity P2M.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

If we find that the PFN is within the P2M as an identity
make sure to tack on the _PAGE_IOMAP flag.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   19 +++++++++++++++----
 1 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d470435..158d07a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -828,7 +828,7 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
        if (val & _PAGE_PRESENT) {
                unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
                pteval_t flags = val & PTE_FLAGS_MASK;
-               unsigned long mfn = pfn_to_mfn(pfn);
+               unsigned long mfn = get_phys_to_machine(pfn);
 
                /*
                 * If there's no mfn for the pfn, then just create an
@@ -839,8 +839,18 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
                if (unlikely(mfn == INVALID_P2M_ENTRY)) {
                        mfn = 0;
                        flags = 0;
+               } else {
+                       /*
+                        * Paramount to do this test _after_ the
+                        * INVALID_P2M_ENTRY as INVALID_P2M_ENTRY &
+                        * IDENTITY_FRAME_BIT resolves to true.
+                        */
+                       mfn &= ~FOREIGN_FRAME_BIT;
+                       if (mfn & IDENTITY_FRAME_BIT) {
+                               mfn &= ~IDENTITY_FRAME_BIT;
+                               flags |= _PAGE_IOMAP;
+                       }
                }
-
                val = ((pteval_t)mfn << PAGE_SHIFT) | flags;
        }
 
@@ -968,8 +978,9 @@ pte_t xen_make_pte_debug(pteval_t pte)
                        (unsigned long)addr, (unsigned long)other_addr);
        } else {
                other_addr = (_pte.pte & PTE_PFN_MASK);
-               WARN((addr == other_addr) && (!io_page),
-                       "0x%lx is missing VM_IO!\n",
+               pteval_t iomap_set = (_pte.pte & PTE_FLAGS_MASK) & _PAGE_IOMAP;
+               WARN((addr == other_addr) && (!io_page) && (!iomap_set),
+                       "0x%lx is missing VM_IO (and wasn't fixed)!\n",
                        (unsigned long)addr);
        }
 
-- 
1.7.1


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