RE: [Xen-devel] [PATCH 6/6] Change MMU_PT_UPDATE_RESERVE_AD to support update page table for foreign domain

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

Keir, this is the updated version, please have a look on it.

Thanks
Yunhong Jiang

Currently MMU_PT_UPDATE_RESERVE_AD support only update page table for current 
domain. This patch add support for foreign domain also.

Signed-off-by: Jiang, Yunhong <yunhong.jiang@xxxxxxxxx>

diff -r 9a74617c4a28 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Tue Jun 30 01:44:30 2009 +0800
+++ b/xen/arch/x86/mm.c Tue Jun 30 01:51:15 2009 +0800
@@ -110,6 +110,7 @@
 #include <asm/hypercall.h>
 #include <asm/shared.h>
 #include <public/memory.h>
+#include <public/sched.h>
 #include <xsm/xsm.h>
 #include <xen/trace.h>
 
@@ -2999,8 +3000,9 @@ int do_mmu_update(
     unsigned long gpfn, gmfn, mfn;
     struct page_info *page;
     int rc = 0, okay = 1, i = 0;
-    unsigned int cmd, done = 0;
-    struct domain *d = current->domain;
+    unsigned int cmd, done = 0, pt_dom;
+    struct domain *d = current->domain, *pt_owner = NULL;
+    struct vcpu *v = current;
     struct domain_mmap_cache mapcache;
 
     if ( unlikely(count & MMU_UPDATE_PREEMPTED) )
@@ -3018,7 +3020,28 @@ int do_mmu_update(
         goto out;
     }
 
-    if ( !set_foreigndom(foreigndom) )
+    pt_dom = foreigndom >> 16;
+    if (pt_dom)
+    {
+        /* the page table belongs to foreign domain */
+        pt_owner = rcu_lock_domain_by_id(pt_dom - 1);
+        if (!pt_owner )
+        {
+            rc = -EINVAL;
+            goto out;
+        }
+        if( !IS_PRIV_FOR(d, pt_owner) )
+        {
+            rc = -ESRCH;
+            goto out;
+        }
+        if (pt_dom == d)
+            rcu_unlock_domain(pt_owner);
+        v = pt_owner->vcpu[0];
+    } else
+        pt_owner = d;
+
+    if ( !set_foreigndom(foreigndom & 0xFFFFU) )
     {
         rc = -ESRCH;
         goto out;
@@ -3059,9 +3082,9 @@ int do_mmu_update(
 
             req.ptr -= cmd;
             gmfn = req.ptr >> PAGE_SHIFT;
-            mfn = gmfn_to_mfn(d, gmfn);
-
-            if ( unlikely(!get_page_from_pagenr(mfn, d)) )
+            mfn = gmfn_to_mfn(pt_owner, gmfn);
+
+            if ( unlikely(!get_page_from_pagenr(mfn, pt_owner)) )
             {
                 MEM_LOG("Could not get page for normal update");
                 break;
@@ -3080,24 +3103,21 @@ int do_mmu_update(
                 {
                     l1_pgentry_t l1e = l1e_from_intpte(req.val);
                     okay = mod_l1_entry(va, l1e, mfn,
-                                        cmd == MMU_PT_UPDATE_PRESERVE_AD,
-                                        current);
+                                        cmd == MMU_PT_UPDATE_PRESERVE_AD, v);
                 }
                 break;
                 case PGT_l2_page_table:
                 {
                     l2_pgentry_t l2e = l2e_from_intpte(req.val);
                     okay = mod_l2_entry(va, l2e, mfn,
-                                        cmd == MMU_PT_UPDATE_PRESERVE_AD,
-                                        current);
+                                        cmd == MMU_PT_UPDATE_PRESERVE_AD, v);
                 }
                 break;
                 case PGT_l3_page_table:
                 {
                     l3_pgentry_t l3e = l3e_from_intpte(req.val);
                     rc = mod_l3_entry(va, l3e, mfn,
-                                      cmd == MMU_PT_UPDATE_PRESERVE_AD, 1,
-                                      current);
+                                      cmd == MMU_PT_UPDATE_PRESERVE_AD, 1, v);
                     okay = !rc;
                 }
                 break;
@@ -3106,8 +3126,7 @@ int do_mmu_update(
                 {
                     l4_pgentry_t l4e = l4e_from_intpte(req.val);
                     rc = mod_l4_entry(va, l4e, mfn,
-                                      cmd == MMU_PT_UPDATE_PRESERVE_AD, 1,
-                                      current);
+                                      cmd == MMU_PT_UPDATE_PRESERVE_AD, 1, v);
                     okay = !rc;
                 }
                 break;
@@ -3115,7 +3134,7 @@ int do_mmu_update(
                 case PGT_writable_page:
                     perfc_incr(writable_mmu_updates);
                     okay = paging_write_guest_entry(
-                        current, va, req.val, _mfn(mfn));
+                        v, va, req.val, _mfn(mfn));
                     break;
                 }
                 page_unlock(page);
@@ -3126,7 +3145,7 @@ int do_mmu_update(
             {
                 perfc_incr(writable_mmu_updates);
                 okay = paging_write_guest_entry(
-                    current, va, req.val, _mfn(mfn));
+                    v, va, req.val, _mfn(mfn));
                 put_page_type(page);
             }
 
@@ -3191,6 +3210,9 @@ int do_mmu_update(
     perfc_add(num_page_updates, i);
 
  out:
+    if (pt_owner && (pt_owner != d))
+        rcu_unlock_domain(pt_owner);
+
     /* Add incremental work we have done to the @done output parameter. */
     if ( unlikely(!guest_handle_is_null(pdone)) )
     {
diff -r 9a74617c4a28 xen/include/public/xen.h
--- a/xen/include/public/xen.h  Tue Jun 30 01:44:30 2009 +0800
+++ b/xen/include/public/xen.h  Tue Jun 30 01:44:33 2009 +0800
@@ -166,10 +166,14 @@ DEFINE_XEN_GUEST_HANDLE(xen_pfn_t);
  * ptr[1:0] specifies the appropriate MMU_* command.
  * 
  * ptr[1:0] == MMU_NORMAL_PT_UPDATE:
- * Updates an entry in a page table. If updating an L1 table, and the new
+ * Updates an entry in a page table.
+ * The page table can be owned by current domain, or a foreign domain. If
+ * the page table belongs to a foreign domain, it should be specified in
+ * upper 16 bits in FD
+ * If updating an L1 table, and the new
  * table entry is valid/present, the mapped frame must belong to the FD, if
- * an FD has been specified. If attempting to map an I/O page then the
- * caller assumes the privilege of the FD.
+ * an foreign domain specified in lower 16 btis in FD. If attempting to map
+ * an I/O page then the caller assumes the privilege of the FD.
  * FD == DOMID_IO: Permit /only/ I/O mappings, at the priv level of the caller.
  * FD == DOMID_XEN: Map restricted areas of Xen's heap space.
  * ptr[:2]  -- Machine address of the page-table entry to modify.


Keir Fraser wrote:
> On 01/06/2009 10:35, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:
> 
>> I think I missed this logic, I just make sure the domain is
>> suspended, but seems be wrong because a suspended domain can still
>> be killed and relinquish resources. So I will add this logic and
>> resend the patch. 
>> 
>> But I'm not sure if we need make sure the guest is suspended/paused
>> during these functions, as exchange a page or pte in flight may
>> cause trouble. Or we can leave it to user space tools, since this
>> situation will not damage xen HV itself.
> 
> The HV should not bother to do the suspend check. It is a higher-level
> problem which should be checked by the tools.
> 
> -- Keir

Attachment: pt_update_v2.patch
Description: pt_update_v2.patch

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel