Re: [PATCH] sun4m: fix setting CPU id when more than one CPU is present

[Philippe Mathieu-Daudé]

On 8/25/21 11:51 AM, Mark Cave-Ayland wrote:
> Commit 24f675cd3b ("sparc/sun4m: Use start-powered-off CPUState property") 
> changed
> the sun4m CPU reset code to use the start-powered-off property and so split 
> the
> creation of the CPU into separate instantiation and realization phases to 
> enable
> the new start-powered-off property to be set.
> 
> This accidentally broke sun4m machines with more than one CPU present since
> sparc_cpu_realizefn() sets a default CPU id, and now that realization occurs 
> after
> calling cpu_sparc_set_id() in cpu_devinit() the CPU id gets reset back to the
> default instead of being uniquely encoded based upon the CPU number. As soon 
> as
> another CPU is brought online, the OS gets confused between them and promptly
> panics.
> 
> Resolve the issue by moving the cpu_sparc_set_id() call in cpu_devinit() to 
> after
> the point where the CPU device has been realized as before.
> 
> Fixes: 24f675cd3b ("sparc/sun4m: Use start-powered-off CPUState property")
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  hw/sparc/sun4m.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/sparc/sun4m.c b/hw/sparc/sun4m.c
> index 42e139849e..7f3a7c0027 100644
> --- a/hw/sparc/sun4m.c
> +++ b/hw/sparc/sun4m.c
> @@ -803,11 +803,11 @@ static void cpu_devinit(const char *cpu_type, unsigned 
> int id,
>      cpu = SPARC_CPU(object_new(cpu_type));
>      env = &cpu->env;
>  
> -    cpu_sparc_set_id(env, id);
>      qemu_register_reset(sun4m_cpu_reset, cpu);
>      object_property_set_bool(OBJECT(cpu), "start-powered-off", id != 0,
>                               &error_fatal);
>      qdev_realize_and_unref(DEVICE(cpu), NULL, &error_fatal);
> +    cpu_sparc_set_id(env, id);
>      *cpu_irqs = qemu_allocate_irqs(cpu_set_irq, cpu, MAX_PILS);
>      env->prom_addr = prom_addr;
>  }

What about directly passing the CPU ID as property (untested):

-- >8 --
Author: Philippe Mathieu-Daudé <f4bug@amsat.org>
Date:   Wed Aug 25 12:26:02 2021 +0200

    sun4m: fix setting CPU id when more than one CPU is present

    Commit 24f675cd3b ("sparc/sun4m: Use start-powered-off CPUState
property") changed
    the sun4m CPU reset code to use the start-powered-off property and
so split the
    creation of the CPU into separate instantiation and realization
phases to enable
    the new start-powered-off property to be set.

    This accidentally broke sun4m machines with more than one CPU
present since
    sparc_cpu_realizefn() sets a default CPU id, and now that
realization occurs after
    calling cpu_sparc_set_id() in cpu_devinit() the CPU id gets reset
back to the
    default instead of being uniquely encoded based upon the CPU number.
As soon as
    another CPU is brought online, the OS gets confused between them and
promptly
    panics.

    Resolve the issue by adding a 'cpu-id' property to CPUSPARCState,
removing
    cpu_sparc_set_id().

    Fixes: 24f675cd3b ("sparc/sun4m: Use start-powered-off CPUState
property")
    Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
    Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

diff --git a/target/sparc/cpu.h b/target/sparc/cpu.h
index ff8ae73002a..78ca0925d25 100644
--- a/target/sparc/cpu.h
+++ b/target/sparc/cpu.h
@@ -262,6 +262,7 @@ struct sparc_def_t {
     uint32_t mmu_cxr_mask;
     uint32_t mmu_sfsr_mask;
     uint32_t mmu_trcr_mask;
+    uint8_t mxcc_cpuid;
     uint32_t mxcc_version;
     uint32_t features;
     uint32_t nwindows;
@@ -583,7 +584,6 @@ void cpu_raise_exception_ra(CPUSPARCState *, int,
uintptr_t) QEMU_NORETURN;

 #ifndef NO_CPU_IO_DEFS
 /* cpu_init.c */
-void cpu_sparc_set_id(CPUSPARCState *env, unsigned int cpu);
 void sparc_cpu_list(void);
 /* mmu_helper.c */
 bool sparc_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
diff --git a/hw/sparc/leon3.c b/hw/sparc/leon3.c
index 7b4dec17211..8189045fdbf 100644
--- a/hw/sparc/leon3.c
+++ b/hw/sparc/leon3.c
@@ -238,8 +238,6 @@ static void leon3_generic_hw_init(MachineState *machine)
     cpu = SPARC_CPU(cpu_create(machine->cpu_type));
     env = &cpu->env;

-    cpu_sparc_set_id(env, 0);
-
     /* Reset data */
     reset_info        = g_malloc0(sizeof(ResetData));
     reset_info->cpu   = cpu;
diff --git a/hw/sparc/sun4m.c b/hw/sparc/sun4m.c
index 42e139849ed..5be2e8e73f2 100644
--- a/hw/sparc/sun4m.c
+++ b/hw/sparc/sun4m.c
@@ -803,10 +803,10 @@ static void cpu_devinit(const char *cpu_type,
unsigned int id,
     cpu = SPARC_CPU(object_new(cpu_type));
     env = &cpu->env;

-    cpu_sparc_set_id(env, id);
     qemu_register_reset(sun4m_cpu_reset, cpu);
     object_property_set_bool(OBJECT(cpu), "start-powered-off", id != 0,
                              &error_fatal);
+    object_property_set_uint(OBJECT(cpu), "cpu-id", id, &error_fatal);
     qdev_realize_and_unref(DEVICE(cpu), NULL, &error_fatal);
     *cpu_irqs = qemu_allocate_irqs(cpu_set_irq, cpu, MAX_PILS);
     env->prom_addr = prom_addr;
diff --git a/target/sparc/cpu.c b/target/sparc/cpu.c
index da6b30ec747..d76929c68c7 100644
--- a/target/sparc/cpu.c
+++ b/target/sparc/cpu.c
@@ -194,13 +194,6 @@ static void sparc_cpu_parse_features(const char
*typename, char *features,
     g_list_free_full(minus_features, g_free);
 }

-void cpu_sparc_set_id(CPUSPARCState *env, unsigned int cpu)
-{
-#if !defined(TARGET_SPARC64)
-    env->mxccregs[7] = ((cpu + 8) & 0xf) << 24;
-#endif
-}
-
 static const sparc_def_t sparc_defs[] = {
 #ifdef TARGET_SPARC64
     {
@@ -754,7 +747,7 @@ static void sparc_cpu_realizefn(DeviceState *dev,
Error **errp)
     env->nwindows = env->def.nwindows;
 #if !defined(TARGET_SPARC64)
     env->mmuregs[0] |= env->def.mmu_version;
-    cpu_sparc_set_id(env, 0);
+    env->mxccregs[7] = ((env->def.mxcc_cpuid + 8) & 0xf) << 24;
     env->mxccregs[7] |= env->def.mxcc_version;
 #else
     env->mmu_version = env->def.mmu_version;
@@ -843,6 +836,7 @@ static Property sparc_cpu_properties[] = {
                          qdev_prop_uint64, target_ulong),
     DEFINE_PROP_UINT32("fpu-version", SPARCCPU, env.def.fpu_version, 0),
     DEFINE_PROP_UINT32("mmu-version", SPARCCPU, env.def.mmu_version, 0),
+    DEFINE_PROP_UINT8("cpu-id", SPARCCPU, env.def.mxcc_cpuid, 0),
     DEFINE_PROP("nwindows", SPARCCPU, env.def.nwindows,
                 qdev_prop_nwindows, uint32_t),
     DEFINE_PROP_END_OF_LIST()
---