diff -BbuNr xen-unstable.hg-orig/xen/arch/x86/hvm/hvm.c xen-unstable.hg-handle_ro/xen/arch/x86/hvm/hvm.c
--- xen-unstable.hg-orig/xen/arch/x86/hvm/hvm.c	2008-07-08 15:52:50.000000000 +0100
+++ xen-unstable.hg-handle_ro/xen/arch/x86/hvm/hvm.c	2008-07-10 11:48:47.074848083 +0100
@@ -1492,6 +1492,18 @@
             return HVMCOPY_bad_gfn_to_mfn;
         ASSERT(mfn_valid(mfn));
 
+        if ( unlikely((flags & HVMCOPY_to_guest) && (p2mt == p2m_ram_ro)) )
+        {
+            static unsigned long lastpage = 0;
+            if ( gfn != lastpage )
+            {
+                lastpage = gfn;
+                gdprintk(XENLOG_DEBUG, "guest attempted write to read-only memory page. "
+                         "page=%#lx, mfn=%#lx\n", (lastpage << PAGE_SHIFT), mfn);
+            }
+            goto nocopy;
+        }
+
         p = (char *)map_domain_page(mfn) + (addr & ~PAGE_MASK);
 
         if ( flags & HVMCOPY_to_guest )
@@ -1506,6 +1518,7 @@
 
         unmap_domain_page(p);
 
+nocopy:        
         addr += count;
         buf  += count;
         todo -= count;
diff -BbuNr xen-unstable.hg-orig/xen/arch/x86/mm/shadow/multi.c xen-unstable.hg-handle_ro/xen/arch/x86/mm/shadow/multi.c
--- xen-unstable.hg-orig/xen/arch/x86/mm/shadow/multi.c	2008-07-08 15:52:50.000000000 +0100
+++ xen-unstable.hg-handle_ro/xen/arch/x86/mm/shadow/multi.c	2008-07-10 11:20:05.455253583 +0100
@@ -3042,6 +3042,8 @@
     int fast_emul = 0;
 #endif
 
+    emul_ctxt.no_write = 0;
+
     SHADOW_PRINTK("d:v=%u:%u va=%#lx err=%u, rip=%lx\n",
                   v->domain->domain_id, v->vcpu_id, va, regs->error_code,
                   regs->rip);
@@ -3344,14 +3346,25 @@
         }
     }
 
-    /* Need to hand off device-model MMIO and writes to read-only
-     * memory to the device model */
-    if ( p2mt == p2m_mmio_dm 
-         || (p2mt == p2m_ram_ro && ft == ft_demand_write) ) 
+    /* Need to hand off device-model MMIO to the device model */
+    if ( p2mt == p2m_mmio_dm ) 
     {
         gpa = guest_walk_to_gpa(&gw);
         goto mmio;
     }
+    /* Log attempts to write to read-only memory */
+    else if (p2mt == p2m_ram_ro && ft == ft_demand_write)
+    {
+        static unsigned long lastpage = 0;
+        if ( (va & PAGE_MASK) != lastpage )
+        {
+            lastpage = (va & PAGE_MASK);
+            gdprintk(XENLOG_DEBUG, "guest attempted write to read-only memory page. "
+                     "va page=%#lx, mfn=%#lx\n", ( va & PAGE_MASK), mfn_x(gmfn));
+        }
+        emul_ctxt.no_write = 1;
+        goto emulate;
+    }
 
     /* In HVM guests, we force CR0.WP always to be set, so that the
      * pagetables are always write-protected.  If the guest thinks
@@ -4776,6 +4789,9 @@
 {
     void *addr;
 
+    if ( sh_ctxt->no_write )
+        return X86EMUL_OKAY;
+
     /* Unaligned writes are only acceptable on HVM */
     if ( (vaddr & (bytes - 1)) && !is_hvm_vcpu(v)  )
         return X86EMUL_UNHANDLEABLE;
diff -BbuNr xen-unstable.hg-orig/xen/arch/x86/mm/shadow/private.h xen-unstable.hg-handle_ro/xen/arch/x86/mm/shadow/private.h
--- xen-unstable.hg-orig/xen/arch/x86/mm/shadow/private.h	2008-07-08 15:52:50.000000000 +0100
+++ xen-unstable.hg-handle_ro/xen/arch/x86/mm/shadow/private.h	2008-07-09 18:44:37.234991121 +0100
@@ -751,6 +751,9 @@
     /* MFNs being written to in write/cmpxchg callbacks */
     mfn_t mfn1, mfn2;
 
+    /* Discard writes */
+    unsigned int no_write; 
+
 #if (SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY)
     /* Special case for avoiding having to verify writes: remember 
      * whether the old value had its low bit (_PAGE_PRESENT) clear. */