Re: [Qemu-arm] [PATCH] hw: add .min_cpus and .default_cpus fields to machine_class

[Emilio G. Cota]

On Mon, Nov 06, 2017 at 12:10:22 -0200, Eduardo Habkost wrote:
> IMO, initialization state doesn't belong to CPUClass.  We already
> have a single accelerator object in MachineState::accelerator,
> and tcg_initialized could be moved to a AccelState::initialized
> field.

I don't know how to cleanly get AccelState from a CPUClass pointer
(as I said I'm not familiar with object code / qom) -- suggestions
welcome! The best I could come up in the limited time I have for
this is to use a static bool, as shown below.


---8<---

Subject: [PATCH] qom: move CPUClass.tcg_initialize to a global

55c3cee ("qom: Introduce CPUClass.tcg_initialize", 2017-10-24)
introduces a per-CPUClass bool that we check so that the target CPU
is initialized for TCG only once. This works well except when
we end up creating more than one CPUClass, in which case we end
up incorrectly initializing TCG more than once, i.e. once for
each CPUClass.

This can be replicated with:
  $ aarch64-softmmu/qemu-system-aarch64 -machine xlnx-zcu102 -smp 6 \
      -global driver=xlnx,,zynqmp,property=has_rpu,value=on
In this case the class name of the "RPUs" is prefixed by "cortex-r5-",
whereas the "regular" CPUs are prefixed by "cortex-a53-". This
results in two CPUClass instances being created.

Fix it by introducing a static variable, so that only the first
target CPU being initialized will initialize the target-dependent
part of TCG, regardless of CPUClass instances.

Fixes: 55c3ceef61fcf06fc98ddc752b7cce788ce7680b
Signed-off-by: Emilio G. Cota <address@hidden>
---
 exec.c            | 5 +++--
 include/qom/cpu.h | 1 -
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/exec.c b/exec.c
index 97a24a8..8b579c0 100644
--- a/exec.c
+++ b/exec.c
@@ -792,11 +792,12 @@ void cpu_exec_initfn(CPUState *cpu)
 void cpu_exec_realizefn(CPUState *cpu, Error **errp)
 {
     CPUClass *cc = CPU_GET_CLASS(cpu);
+    static bool tcg_target_initialized;
 
     cpu_list_add(cpu);
 
-    if (tcg_enabled() && !cc->tcg_initialized) {
-        cc->tcg_initialized = true;
+    if (tcg_enabled() && !tcg_target_initialized) {
+        tcg_target_initialized = true;
         cc->tcg_initialize();
     }
 
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index fa4b0c9..c2fa151 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -209,7 +209,6 @@ typedef struct CPUClass {
     /* Keep non-pointer data at the end to minimize holes.  */
     int gdb_num_core_regs;
     bool gdb_stop_before_watchpoint;
-    bool tcg_initialized;
 } CPUClass;
 
 #ifdef HOST_WORDS_BIGENDIAN
-- 
2.7.4