[Xen-devel] [RFC PATCH 75/84] x86/mm: handle PSE early termination cases in virt_to_mfn_walk().

[<hongyax@xxxxxxxxxx>]

From: Hongyan Xia <hongyax@xxxxxxxxxx>

Signed-off-by: Hongyan Xia <hongyax@xxxxxxxxxx>
---
 xen/arch/x86/mm.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index ab760ecc1f..39ba9f9bf4 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5058,8 +5058,40 @@ l1_pgentry_t *virt_to_xen_l1e(unsigned long v)
 
 unsigned long virt_to_mfn_walk(void *va)
 {
-    l1_pgentry_t *pl1e = virt_to_xen_l1e((unsigned long)(va));
-    unsigned long ret = l1e_get_pfn(*pl1e);
+    unsigned long ret;
+    l3_pgentry_t *pl3e;
+    l2_pgentry_t *pl2e;
+    l1_pgentry_t *pl1e;
+
+    /*
+     * FIXME: This is rather unoptimised, because e.g. virt_to_xen_l2e
+     * recomputes virt_to_xen_l3e again. Clearly one can keep the result and
+     * carry on.
+     */
+
+    pl3e = virt_to_xen_l3e((unsigned long)(va));
+    BUG_ON(!(l3e_get_flags(*pl3e) & _PAGE_PRESENT));
+    if ( l3e_get_flags(*pl3e) & _PAGE_PSE )
+    {
+        ret = l3e_get_pfn(*pl3e);
+        ret |= (((unsigned long)va & ((1UL << L3_PAGETABLE_SHIFT)-1)) >> 
PAGE_SHIFT);
+        unmap_xen_pagetable(pl3e);
+        return ret;
+    }
+
+    pl2e = virt_to_xen_l2e((unsigned long)(va));
+    BUG_ON(!(l2e_get_flags(*pl2e) & _PAGE_PRESENT));
+    if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
+    {
+        ret = l2e_get_pfn(*pl2e);
+        ret |= (((unsigned long)va & ((1UL << L2_PAGETABLE_SHIFT)-1)) >> 
PAGE_SHIFT);
+        unmap_xen_pagetable(pl2e);
+        return ret;
+    }
+
+    pl1e = virt_to_xen_l1e((unsigned long)(va));
+    BUG_ON(!(l1e_get_flags(*pl1e) & _PAGE_PRESENT));
+    ret = l1e_get_pfn(*pl1e);
     unmap_xen_pagetable(pl1e);
     return ret;
 }
-- 
2.17.1


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