[Xen-devel] [PATCH 4/6] xentrace: ARM platform DOMID_XEN mapping support

[Benjamin Sanda <ben.sanda@xxxxxxxxxxxxxxx>]

From: bensanda <ben.sanda@xxxxxxxxxxxxxxx>

Modified xenmem_add_to_physmap_one() to provide support for xentrace on the ARM 
platform. Checks for DOMID_XEN added via new function, get_pg_owner, ported 
from x86 code base. This provides correct calls to rcu_lock_domain() when 
DOMID_XEN is requested. DOMID_XEN checks also adde to skip page to MFN 
translation (xentrace sends a MFN dirrectly and so does not need to be 
translated).

Signed-off-by: Benjamin Sanda <ben.sanda@xxxxxxxxxxxxxxx>
---
 xen/arch/arm/mm.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 54 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 81f9e2e..b1d834f 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -41,6 +41,7 @@
 #include <xen/pfn.h>
 
 struct domain *dom_xen, *dom_io, *dom_cow;
+static struct domain *get_pg_owner(domid_t domid);
 
 /* Static start-of-day pagetables that we use before the allocators
  * are up. These are used by all CPUs during bringup before switching
@@ -1099,7 +1100,8 @@ int xenmem_add_to_physmap_one(
     {
         struct domain *od;
         p2m_type_t p2mt;
-        od = rcu_lock_domain_by_any_id(foreign_domid);
+        od = get_pg_owner(foreign_domid);
+
         if ( od == NULL )
             return -ESRCH;
 
@@ -1132,7 +1134,17 @@ int xenmem_add_to_physmap_one(
             return -EINVAL;
         }
 
-        mfn = page_to_mfn(page);
+        /* If DOMID_XEN then no page to MFN translation is 
+        needed as we already have the MFN directly */
+        if(DOMID_XEN !=od->domain_id)
+        {
+            mfn = page_to_mfn(page);
+        }
+        else
+        {
+            mfn = idx;
+        }
+
         t = p2m_map_foreign;
 
         rcu_unlock_domain(od);
@@ -1312,6 +1324,46 @@ void clear_and_clean_page(struct page_info *page)
     unmap_domain_page(p);
 }
 
+/* Ported from x86 architecture: checks for special domain requests for
+DOMID_XEN or DOMID_IO which must be handled differently then guest domain 
+requests */
+static struct domain *get_pg_owner(domid_t domid)
+{
+    struct domain *pg_owner = NULL, *curr = current->domain;
+
+    if ( likely(domid == DOMID_SELF) )
+    {
+        pg_owner = rcu_lock_current_domain();
+        goto out;
+    }
+
+    if ( unlikely(domid == curr->domain_id) )
+    {
+        goto out;
+    }
+
+    /* check for special domain cases of DOMID_IO or DOMID_XEN which
+    must use rcu_lock_domain() and dom_xen/dom_io as the domid_t */
+    switch ( domid )
+    {
+    case DOMID_IO:
+        pg_owner = rcu_lock_domain(dom_io);
+        break;
+    case DOMID_XEN:
+        pg_owner = rcu_lock_domain(dom_xen);
+        break;
+    default:
+        if ( (pg_owner = rcu_lock_domain_by_id(domid)) == NULL )
+        {
+            break;
+        }
+        break;
+    }
+
+ out:
+    return pg_owner;
+}
+
 /*
  * Local variables:
  * mode: C
-- 
2.7.2


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