[Xen-changelog] [xen-unstable] x86/mm: New mem access type to log access

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
# Date 1323206216 0
# Node ID 38eb74c01d9d9afacdf0c79fcb5555d99719dfa5
# Parent  f24c664557e5e834140833927a5d3f2bab7ca270
x86/mm: New mem access type to log access

This patch adds a new p2m access type, n2rwx. It allows for implement a "log
access" mode in the hypervisor, akin to log dirty but for all types of
accesses. Faults caused by this access mode automatically promote the
access rights of the offending p2m entry, place the event in the ring, and
let the vcpu keep on executing.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Signed-off-by: Adin Scannell <adin@xxxxxxxxxxx>
Acked-by: Tim Deegan <tim@xxxxxxx>
Committed-by: Tim Deegan <tim@xxxxxxx>
---


diff -r f24c664557e5 -r 38eb74c01d9d xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c    Tue Dec 06 21:16:56 2011 +0000
+++ b/xen/arch/x86/hvm/hvm.c    Tue Dec 06 21:16:56 2011 +0000
@@ -1250,6 +1250,7 @@
         switch (p2ma) 
         {
         case p2m_access_n:
+        case p2m_access_n2rwx:
         default:
             violation = access_r || access_w || access_x;
             break;
diff -r f24c664557e5 -r 38eb74c01d9d xen/arch/x86/mm/p2m-ept.c
--- a/xen/arch/x86/mm/p2m-ept.c Tue Dec 06 21:16:56 2011 +0000
+++ b/xen/arch/x86/mm/p2m-ept.c Tue Dec 06 21:16:56 2011 +0000
@@ -111,6 +111,7 @@
     switch (access) 
     {
         case p2m_access_n:
+        case p2m_access_n2rwx:
             entry->r = entry->w = entry->x = 0;
             break;
         case p2m_access_r:
diff -r f24c664557e5 -r 38eb74c01d9d xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c     Tue Dec 06 21:16:56 2011 +0000
+++ b/xen/arch/x86/mm/p2m.c     Tue Dec 06 21:16:56 2011 +0000
@@ -1107,6 +1107,11 @@
         p2m_unlock(p2m);
         return 1;
     }
+    else if ( p2ma == p2m_access_n2rwx )
+    {
+        ASSERT(access_w || access_r || access_x);
+        p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2mt, p2m_access_rwx);
+    }
     p2m_unlock(p2m);
 
     /* Otherwise, check if there is a memory event listener, and send the 
message along */
@@ -1124,10 +1129,13 @@
         }
         else
         {
-            /* A listener is not required, so clear the access restrictions */
-            p2m_lock(p2m);
-            p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2mt, p2m_access_rwx);
-            p2m_unlock(p2m);
+            if ( p2ma != p2m_access_n2rwx )
+            {
+                /* A listener is not required, so clear the access 
restrictions */
+                p2m_lock(p2m);
+                p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2mt, 
p2m_access_rwx);
+                p2m_unlock(p2m);
+            }
             return 1;
         }
 
@@ -1140,9 +1148,12 @@
     req.type = MEM_EVENT_TYPE_ACCESS;
     req.reason = MEM_EVENT_REASON_VIOLATION;
 
-    /* Pause the current VCPU unconditionally */
-    vcpu_pause_nosync(v);
-    req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;    
+    /* Pause the current VCPU */
+    if ( p2ma != p2m_access_n2rwx )
+    {
+        vcpu_pause_nosync(v);
+        req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
+    } 
 
     /* Send request to mem event */
     req.gfn = gfn;
@@ -1157,8 +1168,8 @@
 
     mem_event_put_request(d, &d->mem_event->access, &req);
 
-    /* VCPU paused, mem event request sent */
-    return 0;
+    /* VCPU may be paused, return whether we promoted automatically */
+    return (p2ma == p2m_access_n2rwx);
 }
 
 void p2m_mem_access_resume(struct domain *d)
@@ -1204,6 +1215,7 @@
         p2m_access_wx,
         p2m_access_rwx,
         p2m_access_rx2rw,
+        p2m_access_n2rwx,
         p2m->default_access,
     };
 
diff -r f24c664557e5 -r 38eb74c01d9d xen/include/asm-x86/p2m.h
--- a/xen/include/asm-x86/p2m.h Tue Dec 06 21:16:56 2011 +0000
+++ b/xen/include/asm-x86/p2m.h Tue Dec 06 21:16:56 2011 +0000
@@ -108,6 +108,9 @@
     p2m_access_wx    = 6, 
     p2m_access_rwx   = 7,
     p2m_access_rx2rw = 8, /* Special: page goes from RX to RW on write */
+    p2m_access_n2rwx = 9, /* Special: page goes from N to RWX on access, *
+                           * generates an event but does not pause the
+                           * vcpu */
 
     /* NOTE: Assumed to be only 4 bits right now */
 } p2m_access_t;
diff -r f24c664557e5 -r 38eb74c01d9d xen/include/public/hvm/hvm_op.h
--- a/xen/include/public/hvm/hvm_op.h   Tue Dec 06 21:16:56 2011 +0000
+++ b/xen/include/public/hvm/hvm_op.h   Tue Dec 06 21:16:56 2011 +0000
@@ -174,6 +174,9 @@
     HVMMEM_access_rwx,
     HVMMEM_access_rx2rw,       /* Page starts off as r-x, but automatically
                                 * change to r-w on a write */
+    HVMMEM_access_n2rwx,       /* Log access: starts off as n, automatically 
+                                * goes to rwx, generating an event without
+                                * pausing the vcpu */
     HVMMEM_access_default      /* Take the domain default */
 } hvmmem_access_t;
 /* Notify that a region of memory is to have specific access types */

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