m68k: virt: correctly set the initial PC

[PATCH] m68k: virt: correctly set the initial PC

Posted by Laurent Vivier 2 years, 11 months ago

Set initial PC to the entry of the loaded kernel.

This fixes kernel reboot with "-kernel" parameter.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 hw/m68k/virt.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
index e9a5d4c69b97..4fb3a7ebf0f2 100644
--- a/hw/m68k/virt.c
+++ b/hw/m68k/virt.c
@@ -88,14 +88,21 @@
 #define VIRT_VIRTIO_MMIO_BASE 0xff010000     /* MMIO: 0xff010000 - 0xff01ffff */
 #define VIRT_VIRTIO_IRQ_BASE  PIC_IRQ(2, 1)  /* PIC: 2, 3, 4, 5, IRQ: ALL */
 
+typedef struct {
+    M68kCPU *cpu;
+    hwaddr initial_pc;
+    hwaddr initial_stack;
+} ResetInfo;
+
 static void main_cpu_reset(void *opaque)
 {
-    M68kCPU *cpu = opaque;
+    ResetInfo *reset_info = opaque;
+    M68kCPU *cpu = reset_info->cpu;
     CPUState *cs = CPU(cpu);
 
     cpu_reset(cs);
-    cpu->env.aregs[7] = ldl_phys(cs->as, 0);
-    cpu->env.pc = ldl_phys(cs->as, 4);
+    cpu->env.aregs[7] = reset_info->initial_stack;
+    cpu->env.pc = reset_info->initial_pc;
 }
 
 static void virt_init(MachineState *machine)
@@ -116,6 +123,7 @@ static void virt_init(MachineState *machine)
     SysBusDevice *sysbus;
     hwaddr io_base;
     int i;
+    ResetInfo *reset_info;
 
     if (ram_size > 3399672 * KiB) {
         /*
@@ -127,9 +135,13 @@ static void virt_init(MachineState *machine)
         exit(1);
     }
 
+    reset_info = g_malloc0(sizeof(ResetInfo));
+
     /* init CPUs */
     cpu = M68K_CPU(cpu_create(machine->cpu_type));
-    qemu_register_reset(main_cpu_reset, cpu);
+
+    reset_info->cpu = cpu;
+    qemu_register_reset(main_cpu_reset, reset_info);
 
     /* RAM */
     memory_region_add_subregion(get_system_memory(), 0, machine->ram);
@@ -209,7 +221,7 @@ static void virt_init(MachineState *machine)
             error_report("could not load kernel '%s'", kernel_filename);
             exit(1);
         }
-        stl_phys(cs->as, 4, elf_entry); /* reset initial PC */
+        reset_info->initial_pc = elf_entry;
         parameters_base = (high + 1) & ~1;
 
         BOOTINFO1(cs->as, parameters_base, BI_MACHTYPE, MACH_VIRT);
-- 
2.31.1

Re: [PATCH] m68k: virt: correctly set the initial PC

Posted by Philippe Mathieu-Daudé 2 years, 11 months ago

On 5/4/21 3:18 PM, Laurent Vivier wrote:
> Set initial PC to the entry of the loaded kernel.
> 
> This fixes kernel reboot with "-kernel" parameter.
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  hw/m68k/virt.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
> index e9a5d4c69b97..4fb3a7ebf0f2 100644
> --- a/hw/m68k/virt.c
> +++ b/hw/m68k/virt.c
> @@ -88,14 +88,21 @@
>  #define VIRT_VIRTIO_MMIO_BASE 0xff010000     /* MMIO: 0xff010000 - 0xff01ffff */
>  #define VIRT_VIRTIO_IRQ_BASE  PIC_IRQ(2, 1)  /* PIC: 2, 3, 4, 5, IRQ: ALL */
>  
> +typedef struct {
> +    M68kCPU *cpu;
> +    hwaddr initial_pc;
> +    hwaddr initial_stack;
> +} ResetInfo;
> +
>  static void main_cpu_reset(void *opaque)
>  {
> -    M68kCPU *cpu = opaque;
> +    ResetInfo *reset_info = opaque;
> +    M68kCPU *cpu = reset_info->cpu;
>      CPUState *cs = CPU(cpu);
>  
>      cpu_reset(cs);
> -    cpu->env.aregs[7] = ldl_phys(cs->as, 0);
> -    cpu->env.pc = ldl_phys(cs->as, 4);
> +    cpu->env.aregs[7] = reset_info->initial_stack;
> +    cpu->env.pc = reset_info->initial_pc;
>  }
>  
>  static void virt_init(MachineState *machine)
> @@ -116,6 +123,7 @@ static void virt_init(MachineState *machine)
>      SysBusDevice *sysbus;
>      hwaddr io_base;
>      int i;
> +    ResetInfo *reset_info;
>  
>      if (ram_size > 3399672 * KiB) {
>          /*
> @@ -127,9 +135,13 @@ static void virt_init(MachineState *machine)
>          exit(1);
>      }
>  
> +    reset_info = g_malloc0(sizeof(ResetInfo));
> +
>      /* init CPUs */
>      cpu = M68K_CPU(cpu_create(machine->cpu_type));
> -    qemu_register_reset(main_cpu_reset, cpu);
> +
> +    reset_info->cpu = cpu;
> +    qemu_register_reset(main_cpu_reset, reset_info);
>  
>      /* RAM */
>      memory_region_add_subregion(get_system_memory(), 0, machine->ram);
> @@ -209,7 +221,7 @@ static void virt_init(MachineState *machine)
>              error_report("could not load kernel '%s'", kernel_filename);
>              exit(1);
>          }
> -        stl_phys(cs->as, 4, elf_entry); /* reset initial PC */
> +        reset_info->initial_pc = elf_entry;

Missing the stack?

           reset_info->initial_stack = ldl_phys(cs->as, 0);

>          parameters_base = (high + 1) & ~1;
>  
>          BOOTINFO1(cs->as, parameters_base, BI_MACHTYPE, MACH_VIRT);
>

Re: [PATCH] m68k: virt: correctly set the initial PC

Posted by Laurent Vivier 2 years, 11 months ago

Le 04/05/2021 à 16:13, Philippe Mathieu-Daudé a écrit :
> On 5/4/21 3:18 PM, Laurent Vivier wrote:
>> Set initial PC to the entry of the loaded kernel.
>>
>> This fixes kernel reboot with "-kernel" parameter.
>>
>> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
>> ---
>>  hw/m68k/virt.c | 22 +++++++++++++++++-----
>>  1 file changed, 17 insertions(+), 5 deletions(-)
>>
>> diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
>> index e9a5d4c69b97..4fb3a7ebf0f2 100644
>> --- a/hw/m68k/virt.c
>> +++ b/hw/m68k/virt.c
>> @@ -88,14 +88,21 @@
>>  #define VIRT_VIRTIO_MMIO_BASE 0xff010000     /* MMIO: 0xff010000 - 0xff01ffff */
>>  #define VIRT_VIRTIO_IRQ_BASE  PIC_IRQ(2, 1)  /* PIC: 2, 3, 4, 5, IRQ: ALL */
>>  
>> +typedef struct {
>> +    M68kCPU *cpu;
>> +    hwaddr initial_pc;
>> +    hwaddr initial_stack;
>> +} ResetInfo;
>> +
>>  static void main_cpu_reset(void *opaque)
>>  {
>> -    M68kCPU *cpu = opaque;
>> +    ResetInfo *reset_info = opaque;
>> +    M68kCPU *cpu = reset_info->cpu;
>>      CPUState *cs = CPU(cpu);
>>  
>>      cpu_reset(cs);
>> -    cpu->env.aregs[7] = ldl_phys(cs->as, 0);
>> -    cpu->env.pc = ldl_phys(cs->as, 4);
>> +    cpu->env.aregs[7] = reset_info->initial_stack;
>> +    cpu->env.pc = reset_info->initial_pc;
>>  }
>>  
>>  static void virt_init(MachineState *machine)
>> @@ -116,6 +123,7 @@ static void virt_init(MachineState *machine)
>>      SysBusDevice *sysbus;
>>      hwaddr io_base;
>>      int i;
>> +    ResetInfo *reset_info;
>>  
>>      if (ram_size > 3399672 * KiB) {
>>          /*
>> @@ -127,9 +135,13 @@ static void virt_init(MachineState *machine)
>>          exit(1);
>>      }
>>  
>> +    reset_info = g_malloc0(sizeof(ResetInfo));
>> +
>>      /* init CPUs */
>>      cpu = M68K_CPU(cpu_create(machine->cpu_type));
>> -    qemu_register_reset(main_cpu_reset, cpu);
>> +
>> +    reset_info->cpu = cpu;
>> +    qemu_register_reset(main_cpu_reset, reset_info);
>>  
>>      /* RAM */
>>      memory_region_add_subregion(get_system_memory(), 0, machine->ram);
>> @@ -209,7 +221,7 @@ static void virt_init(MachineState *machine)
>>              error_report("could not load kernel '%s'", kernel_filename);
>>              exit(1);
>>          }
>> -        stl_phys(cs->as, 4, elf_entry); /* reset initial PC */
>> +        reset_info->initial_pc = elf_entry;
> Missing the stack?
>
>            reset_info->initial_stack = ldl_phys(cs->as, 0);

No, as it's a g_malloc0(), initial_stack is set to 0, so aregs[7] (SP) will be reset to 0 on reboot.
We could also set it to  ram_size if we want something usable, but it's not needed for the kernel
entry point.

Thanks,

Laurent

Re: [PATCH] m68k: virt: correctly set the initial PC

Posted by Philippe Mathieu-Daudé 2 years, 11 months ago

On 5/4/21 4:20 PM, Laurent Vivier wrote:
> Le 04/05/2021 à 16:13, Philippe Mathieu-Daudé a écrit :
>> On 5/4/21 3:18 PM, Laurent Vivier wrote:
>>> Set initial PC to the entry of the loaded kernel.
>>>
>>> This fixes kernel reboot with "-kernel" parameter.
>>>
>>> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
>>> ---
>>>  hw/m68k/virt.c | 22 +++++++++++++++++-----
>>>  1 file changed, 17 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
>>> index e9a5d4c69b97..4fb3a7ebf0f2 100644
>>> --- a/hw/m68k/virt.c
>>> +++ b/hw/m68k/virt.c
>>> @@ -88,14 +88,21 @@
>>>  #define VIRT_VIRTIO_MMIO_BASE 0xff010000     /* MMIO: 0xff010000 - 0xff01ffff */
>>>  #define VIRT_VIRTIO_IRQ_BASE  PIC_IRQ(2, 1)  /* PIC: 2, 3, 4, 5, IRQ: ALL */
>>>  
>>> +typedef struct {
>>> +    M68kCPU *cpu;
>>> +    hwaddr initial_pc;
>>> +    hwaddr initial_stack;
>>> +} ResetInfo;
>>> +
>>>  static void main_cpu_reset(void *opaque)
>>>  {
>>> -    M68kCPU *cpu = opaque;
>>> +    ResetInfo *reset_info = opaque;
>>> +    M68kCPU *cpu = reset_info->cpu;
>>>      CPUState *cs = CPU(cpu);
>>>  
>>>      cpu_reset(cs);
>>> -    cpu->env.aregs[7] = ldl_phys(cs->as, 0);
>>> -    cpu->env.pc = ldl_phys(cs->as, 4);
>>> +    cpu->env.aregs[7] = reset_info->initial_stack;
>>> +    cpu->env.pc = reset_info->initial_pc;
>>>  }
>>>  
>>>  static void virt_init(MachineState *machine)
>>> @@ -116,6 +123,7 @@ static void virt_init(MachineState *machine)
>>>      SysBusDevice *sysbus;
>>>      hwaddr io_base;
>>>      int i;
>>> +    ResetInfo *reset_info;
>>>  
>>>      if (ram_size > 3399672 * KiB) {
>>>          /*
>>> @@ -127,9 +135,13 @@ static void virt_init(MachineState *machine)
>>>          exit(1);
>>>      }
>>>  
>>> +    reset_info = g_malloc0(sizeof(ResetInfo));
>>> +
>>>      /* init CPUs */
>>>      cpu = M68K_CPU(cpu_create(machine->cpu_type));
>>> -    qemu_register_reset(main_cpu_reset, cpu);
>>> +
>>> +    reset_info->cpu = cpu;
>>> +    qemu_register_reset(main_cpu_reset, reset_info);
>>>  
>>>      /* RAM */
>>>      memory_region_add_subregion(get_system_memory(), 0, machine->ram);
>>> @@ -209,7 +221,7 @@ static void virt_init(MachineState *machine)
>>>              error_report("could not load kernel '%s'", kernel_filename);
>>>              exit(1);
>>>          }
>>> -        stl_phys(cs->as, 4, elf_entry); /* reset initial PC */
>>> +        reset_info->initial_pc = elf_entry;
>> Missing the stack?
>>
>>            reset_info->initial_stack = ldl_phys(cs->as, 0);
> 
> No, as it's a g_malloc0(), initial_stack is set to 0, so aregs[7] (SP) will be reset to 0 on reboot.
> We could also set it to  ram_size if we want something usable, but it's not needed for the kernel
> entry point.

Indeed I missed g_malloc*0*.

It would be clearer to use g_malloc() and explicitly set the initial
stack IMHO.

> 
> Thanks,
> 
> Laurent
> 
>