[PATCH 02/11] exec: Add new MemoryDebugOps.

[Ashish Kalra <Ashish.Kalra@xxxxxxx>]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

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.

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

Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 include/exec/memory.h | 11 +++++++++++
 softmmu/physmem.c     | 24 ++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index aff6ef7605..73deb4b456 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2394,6 +2394,17 @@ 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;
+
+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 a9adedb9f8..057d6d4ce1 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -166,6 +166,18 @@ struct DirtyBitmapSnapshot {
     unsigned long dirty[];
 };
 
+static const MemoryDebugOps default_debug_ops = {
+    .read = address_space_read,
+    .write = address_space_write_rom
+};
+
+static const MemoryDebugOps *debug_ops = &default_debug_ops;
+
+void address_space_set_debug_ops(const MemoryDebugOps *ops)
+{
+    debug_ops = ops;
+}
+
 static void phys_map_node_reserve(PhysPageMap *map, unsigned nodes)
 {
     static unsigned alloc_hint = 16;
@@ -3407,6 +3419,10 @@ 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;
@@ -3415,11 +3431,11 @@ 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 = 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 = debug_ops->read(cpu->cpu_ases[asidx].as, phys_addr,
+                                  attrs, buf, l);
         }
         if (res != MEMTX_OK) {
             return -1;
-- 
2.17.1