[PATCH v4 07/10] xen/p2m: put reference for superpage

[Penny Zheng <Penny.Zheng@xxxxxxx>]

We are doing foreign memory mapping for static shared memory, and
there is a great possibility that it could be super mapped.
But today, p2m_put_l3_page could not handle superpages.

This commits implements a new function p2m_put_superpage to handle superpages,
specifically for helping put extra references for foreign superpages.

Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
---
v1 -> v2:
- new commit
---
v2 -> v3:
- rebase and no change
---
v3 -> v4:
rebase and no change
---
 xen/arch/arm/p2m.c | 58 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 43 insertions(+), 15 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index de32a2d638..b7b3db005e 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -851,17 +851,9 @@ static int p2m_mem_access_radix_set(struct p2m_domain 
*p2m, gfn_t gfn,
     return rc;
 }
 
-/*
- * Put any references on the single 4K page referenced by pte.
- * TODO: Handle superpages, for now we only take special references for leaf
- * pages (specifically foreign ones, which can't be super mapped today).
- */
-static void p2m_put_l3_page(const lpae_t pte)
+/* Put any references on the single 4K page referenced by mfn. */
+static void p2m_put_l3_page(mfn_t mfn, unsigned type)
 {
-    mfn_t mfn = lpae_get_mfn(pte);
-
-    ASSERT(p2m_is_valid(pte));
-
     /*
      * TODO: Handle other p2m types
      *
@@ -869,16 +861,53 @@ static void p2m_put_l3_page(const lpae_t pte)
      * flush the TLBs if the page is reallocated before the end of
      * this loop.
      */
-    if ( p2m_is_foreign(pte.p2m.type) )
+    if ( p2m_is_foreign(type) )
     {
         ASSERT(mfn_valid(mfn));
         put_page(mfn_to_page(mfn));
     }
     /* Detect the xenheap page and mark the stored GFN as invalid. */
-    else if ( p2m_is_ram(pte.p2m.type) && is_xen_heap_mfn(mfn) )
+    else if ( p2m_is_ram(type) && is_xen_heap_mfn(mfn) )
         page_set_xenheap_gfn(mfn_to_page(mfn), INVALID_GFN);
 }
 
+/* Put any references on the superpage referenced by mfn. */
+static void p2m_put_superpage(mfn_t mfn, unsigned int next_level, unsigned 
type)
+{
+    unsigned int i;
+    unsigned int level_order = XEN_PT_LEVEL_ORDER(next_level);
+
+    for ( i = 0; i < XEN_PT_LPAE_ENTRIES; i++ )
+    {
+        if ( next_level == 3 )
+            p2m_put_l3_page(mfn, type);
+        else
+            p2m_put_superpage(mfn, next_level + 1, type);
+
+        mfn = mfn_add(mfn, 1 << level_order);
+    }
+}
+
+/* Put any references on the page referenced by pte. */
+static void p2m_put_page(const lpae_t pte, unsigned int level)
+{
+    mfn_t mfn = lpae_get_mfn(pte);
+
+    ASSERT(p2m_is_valid(pte));
+
+    /*
+     * We are either having a first level 1G superpage or a
+     * second level 2M superpage.
+     */
+    if ( p2m_is_superpage(pte, level) )
+        return p2m_put_superpage(mfn, level + 1, pte.p2m.type);
+    else
+    {
+        ASSERT(level == 3);
+        return p2m_put_l3_page(mfn, pte.p2m.type);
+    }
+}
+
 /* Free lpae sub-tree behind an entry */
 static void p2m_free_entry(struct p2m_domain *p2m,
                            lpae_t entry, unsigned int level)
@@ -907,9 +936,8 @@ static void p2m_free_entry(struct p2m_domain *p2m,
 #endif
 
         p2m->stats.mappings[level]--;
-        /* Nothing to do if the entry is a super-page. */
-        if ( level == 3 )
-            p2m_put_l3_page(entry);
+        p2m_put_page(entry, level);
+
         return;
     }
 
-- 
2.25.1