[RFC][PATCH v1 06/10] Introduce new MemoryDebugOps which hook into guest virtual and physical memory debug interfaces such as cpu_memory_rw_debug, to allow vendor specific assist/hooks for debugging and delegating accessing the guest memory. This is required for example in case of AMD SEV platform where the guest memory is encrypted and a SEV specific debug assist/hook will be required to access the guest memory.

[Yuan Yao <yuan.yao@xxxxxxxxxxxxxxx>]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

The MemoryDebugOps are used by cpu_memory_rw_debug() and default to
address_space_read and address_space_write_rom.

Yuan Yao: Exports the physical_memory_debug_ops variable for functions
in target/i386/helper.c

Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Yuan Yao <yuan.yao@xxxxxxxxx>

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 7e6fdcb8e4..0250b50beb 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2498,6 +2498,20 @@ MemTxResult address_space_write_cached_slow(MemoryRegionCache *cache,
                                             hwaddr addr, const void *buf,
                                             hwaddr len);
 
+typedef struct MemoryDebugOps {
+    MemTxResult (*read)(AddressSpace *as, hwaddr phys_addr,
+                        MemTxAttrs attrs, void *buf,
+                        hwaddr len);
+    MemTxResult (*write)(AddressSpace *as, hwaddr phys_addr,
+                         MemTxAttrs attrs, const void *buf,
+                         hwaddr len);
+} MemoryDebugOps;
+
+// Export for functions in target/i386/helper.c
+extern const MemoryDebugOps *physical_memory_debug_ops;
+
+void address_space_set_debug_ops(const MemoryDebugOps *ops);
+
 static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
 {
     if (is_write) {
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 85034d9c11..c8029f69ad 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -171,6 +171,18 @@ struct DirtyBitmapSnapshot {
     unsigned long dirty[];
 };
 
+static const MemoryDebugOps default_debug_ops = {
+    .read = address_space_read,
+    .write = address_space_write_rom
+};
+
+const MemoryDebugOps *physical_memory_debug_ops = &default_debug_ops;
+
+void address_space_set_debug_ops(const MemoryDebugOps *ops)
+{
+    physical_memory_debug_ops = ops;
+}
+
 static void phys_map_node_reserve(PhysPageMap *map, unsigned nodes)
 {
     static unsigned alloc_hint = 16;
@@ -3396,6 +3408,10 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
         page = addr & TARGET_PAGE_MASK;
         phys_addr = cpu_get_phys_page_attrs_debug(cpu, page, &attrs);
         asidx = cpu_asidx_from_attrs(cpu, attrs);
+
+        /* set debug attrs to indicate memory access is from the debugger */
+        attrs.debug = 1;
+
         /* if no physical page mapped, return an error */
         if (phys_addr == -1)
             return -1;
@@ -3404,11 +3420,13 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
             l = len;
         phys_addr += (addr & ~TARGET_PAGE_MASK);
         if (is_write) {
-            res = address_space_write_rom(cpu->cpu_ases[asidx].as, phys_addr,
-                                          attrs, buf, l);
+            res = physical_memory_debug_ops->write(cpu->cpu_ases[asidx].as,
+                                                   phys_addr,
+                                                   attrs, buf, l);
         } else {
-            res = address_space_read(cpu->cpu_ases[asidx].as, phys_addr,
-                                     attrs, buf, l);
+            res = physical_memory_debug_ops->read(cpu->cpu_ases[asidx].as,
+                                                  phys_addr,
+                                                  attrs, buf, l);
         }
         if (res != MEMTX_OK) {
             return -1;
-- 
2.20.1