[PATCH v6 07/10] xen/arm: Handle remove foreign mapping

[Julien Grall <julien.grall@linaro.org>]

Modify get_page_from_gfn to take reference on foreign mapping. This will avoid
specific handling in the common code.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

---
    Changes in v6:
        - Use pte.p2m.base instead of arithmetics
        - We don't need to clean pte where valid == 0 (save time)
    Changes in v4.2:
        - get_page_from_gfn: move foreign checking before get_page
        - add assert fdom != dom
    Changes in v4.1:
        - Remove specific p2m handling in common code
        - Handle foreign mapping in get_page_from_gfn
    Changes in v4:
        - Split patch #6 from dom0 pvh series v6.2 to retrieve only common
        code.
        - Rework commit title
        - Rename xen_rem_foreign_from_p2m in p2m_remove_foreign
        - Get the mfn from the pte. We are not sure that maddr given in
        parameters is valid
    Changes in v3:
        - Move put_page in create_p2m_entries
        - Move xenmem_rem_foreign_from_p2m in arch/arm/p2m.c
    Changes in v2:
        - Introduce the patch
---
 xen/arch/arm/p2m.c        |   15 +++++++++++++--
 xen/include/asm-arm/p2m.h |   12 ++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index bc32935..410acb6 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -328,10 +328,21 @@ static int create_p2m_entries(struct domain *d,
                 break;
             case REMOVE:
                 {
-                    lpae_t pte;
+                    lpae_t pte = third[third_table_offset(addr)];
+                    unsigned long mfn = pte.p2m.base;
+
+                    if ( !pte.p2m.valid )
+                        break;
+
+                    /* TODO: Handle other p2m type */
+                    if ( p2m_is_foreign(pte.p2m.type) )
+                    {
+                        ASSERT(mfn_valid(mfn));
+                        put_page(mfn_to_page(mfn));
+                    }
+
                     memset(&pte, 0x00, sizeof(pte));
                     write_pte(&third[third_table_offset(addr)], pte);
-                    maddr += PAGE_SIZE;
                 }
                 break;
         }
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index 0eb07a8..5ccfa7f 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -122,6 +122,18 @@ static inline struct page_info *get_page_from_gfn(
     if ( !mfn_valid(mfn) )
         return NULL;
     page = mfn_to_page(mfn);
+
+    /* get_page won't work on foreign mapping because the page doesn't
+     * belong to the current domain.
+     */
+    if ( p2mt == p2m_map_foreign )
+    {
+        struct domain *fdom = page_get_owner_and_reference(page);
+        ASSERT(fdom != NULL);
+        ASSERT(fdom != d);
+        return page;
+    }
+
     if ( !get_page(page, d) )
         return NULL;
     return page;
-- 
1.7.10.4