Re: [PATCH 2/3] hw/intc: Add NULL pointer check on LoongArch ipi device

[Philippe Mathieu-Daudé]

On 6/4/23 12:00, Song Gao wrote:

When ipi mailbox is used, cpu index is decoded from iocsr register.
cpu maybe does not exist. This patch adss NULL pointer check on
ipi device.

How can that happens from a guest vcpu context?

Signed-off-by: Song Gao <gaos...@loongson.cn>
---
  hw/intc/loongarch_ipi.c | 31 +++++++++++++++++++------------
  1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/hw/intc/loongarch_ipi.c b/hw/intc/loongarch_ipi.c
index 0563d83a35..39e899df46 100644
--- a/hw/intc/loongarch_ipi.c
+++ b/hw/intc/loongarch_ipi.c
@@ -86,11 +86,12 @@ static void ipi_send(uint64_t val)
      /* IPI status vector */
      data = 1 << (val & 0x1f);
      cs = qemu_get_cpu(cpuid);
-    cpu = LOONGARCH_CPU(cs);
-    env = &cpu->env;
-    address_space_stl(&env->address_space_iocsr, 0x1008,
-                      data, MEMTXATTRS_UNSPECIFIED, NULL);
-
+    if (cs) {
+        cpu = LOONGARCH_CPU(cs);
+        env = &cpu->env;
+        address_space_stl(&env->address_space_iocsr, 0x1008,
+                          data, MEMTXATTRS_UNSPECIFIED, NULL);
+    }

Is that the hardware behavior?

Could logging the invalid cpuid request be useful?

       else {

           //log or trace event here
       }

  }