[Qemu-devel] [PATCH] fw_cfg_mem: add read memory region callback

[Li Qiang <liq3ea@gmail.com>]

The write/read should be paired, this can avoid the
NULL-deref while the guest reads the fw_cfg port.

Signed-off-by: Li Qiang <liq3ea@gmail.com>
---
 hw/nvram/fw_cfg.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index d79a568f54..6de7809f1a 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -434,6 +434,11 @@ static bool fw_cfg_data_mem_valid(void *opaque, hwaddr addr,
     return addr == 0;
 }
 
+static uint64_t fw_cfg_ctl_mem_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0;
+}
+
 static void fw_cfg_ctl_mem_write(void *opaque, hwaddr addr,
                                  uint64_t value, unsigned size)
 {
@@ -468,6 +473,7 @@ static bool fw_cfg_comb_valid(void *opaque, hwaddr addr,
 }
 
 static const MemoryRegionOps fw_cfg_ctl_mem_ops = {
+    .read = fw_cfg_ctl_mem_read,
     .write = fw_cfg_ctl_mem_write,
     .endianness = DEVICE_BIG_ENDIAN,
     .valid.accepts = fw_cfg_ctl_mem_valid,
-- 
2.11.0