arch/tile: don't set the homecache of a PTE unless appropriate

We make sure not to try to set the home for an MMIO PTE (on tilegx)
or a PTE that isn't referencing memory managed by Linux.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/arch/tile/mm/pgtable.c b/arch/tile/mm/pgtable.c
index 87303693a072..6b9a109c3e31 100644
--- a/arch/tile/mm/pgtable.c
+++ b/arch/tile/mm/pgtable.c
@@ -469,10 +469,18 @@ void __set_pte(pte_t *ptep, pte_t pte)
 
 void set_pte(pte_t *ptep, pte_t pte)
 {
-        struct page *page = pfn_to_page(pte_pfn(pte));
-
-        /* Update the home of a PTE if necessary */
-        pte = pte_set_home(pte, page_home(page));
+        if (pte_present(pte) &&
+            (!CHIP_HAS_MMIO() || hv_pte_get_mode(pte) != HV_PTE_MODE_MMIO)) {
+                /* The PTE actually references physical memory. */
+                unsigned long pfn = pte_pfn(pte);
+                if (pfn_valid(pfn)) {
+                        /* Update the home of the PTE from the struct page. */
+                        pte = pte_set_home(pte, page_home(pfn_to_page(pfn)));
+                } else if (hv_pte_get_mode(pte) == 0) {
+                        /* remap_pfn_range(), etc, must supply PTE mode. */
+                        panic("set_pte(): out-of-range PFN and mode 0\n");
+                }
+        }
 
         __set_pte(ptep, pte);
 }