[Xen-devel] [PATCH] vmx-mmio-2pages.patch

[Arun Sharma <arun.sharma@xxxxxxxxx>]

Handle the case where the MMIO instruction crosses a page boundary.

Signed-off-by: Arun Sharma <arun.sharma@xxxxxxxxx>

--- 1.21/xen/arch/x86/vmx_platform.c    2005-05-27 12:02:09 -07:00
+++ edited/arch/x86/vmx_platform.c      2005-06-01 13:45:41 -07:00
@@ -406,35 +406,49 @@
     return DECODE_failure;
 }
 
-int inst_copy_from_guest(unsigned char *buf, unsigned long guest_eip, int 
inst_len)
+int inst_copy_from_guest(unsigned char *buf, unsigned long guest_eip,
+                         int inst_len)
 {
     l1_pgentry_t gpte;
     unsigned long mfn;
     unsigned long ma;
     unsigned char * inst_start;
+    int remaining = 0;
         
     if (inst_len > MAX_INST_LEN || inst_len <= 0) {
         return 0;
     }
 
-    if ((guest_eip & PAGE_MASK) == ((guest_eip + inst_len) & PAGE_MASK)) {
-        if (vmx_paging_enabled(current)) {
-                gpte = gva_to_gpte(guest_eip);
-                mfn = phys_to_machine_mapping(l1e_get_pfn(gpte));
-        } else {
-                mfn = phys_to_machine_mapping(guest_eip >> PAGE_SHIFT);
+    if (vmx_paging_enabled(current)) {
+        gpte = gva_to_gpte(guest_eip);
+        mfn = phys_to_machine_mapping(l1e_get_pfn(gpte));
+        /* Does this cross a page boundary ? */
+        if ((guest_eip & PAGE_MASK) != ((guest_eip + inst_len) & PAGE_MASK)) {
+            remaining = (guest_eip + inst_len) & ~PAGE_MASK;
+            inst_len -= remaining;
         }
-        ma = (mfn << PAGE_SHIFT) | (guest_eip & (PAGE_SIZE - 1));
+
+    } else {
+        mfn = phys_to_machine_mapping(guest_eip >> PAGE_SHIFT);
+    }
+    ma = (mfn << PAGE_SHIFT) | (guest_eip & (PAGE_SIZE - 1));
+    inst_start = (unsigned char *)map_domain_mem(ma);
+                
+    memcpy((char *)buf, inst_start, inst_len);
+    unmap_domain_mem(inst_start);
+
+    if (remaining) {
+        gpte = gva_to_gpte(guest_eip+inst_len+remaining);
+        mfn = phys_to_machine_mapping(l1e_get_pfn(gpte));
+
+        ma = (mfn << PAGE_SHIFT);
         inst_start = (unsigned char *)map_domain_mem(ma);
                 
-        memcpy((char *)buf, inst_start, inst_len);
+        memcpy((char *)buf+inst_len, inst_start, remaining);
         unmap_domain_mem(inst_start);
-    } else {
-        // Todo: In two page frames
-        BUG();
+
     }
-        
-    return inst_len;
+    return inst_len+remaining;
 }
 
 static void init_instruction(struct instruction *mmio_inst)

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