[PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Zhang Chen]

Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
is mistakenly set to the default AARCH64 target.

Signed-off-by: Zhang Chen <zhangckid@gmail.com>
---
 hw/arm/virt.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index a96452f17a..63649e9543 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -3178,9 +3178,10 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
     mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
 #ifdef CONFIG_TCG
     mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
-#else
+#ifdef TARGET_AARCH64
     mc->default_cpu_type = ARM_CPU_TYPE_NAME("max");
-#endif
+#endif /* TARGET_AARCH64 */
+#endif /* CONFIG_TCG */
     mc->valid_cpu_types = valid_cpu_types;
     mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
     mc->kvm_type = virt_kvm_type;
-- 
2.49.0

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Richard Henderson]

On 4/2/25 06:54, Zhang Chen wrote:
> Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
> is mistakenly set to the default AARCH64 target.

This is the correct backward compatible setting.
In essence, it means that you *must* supply a -cpu argument.


r~

> 
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>   hw/arm/virt.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index a96452f17a..63649e9543 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -3178,9 +3178,10 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
>       mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
>   #ifdef CONFIG_TCG
>       mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
> -#else
> +#ifdef TARGET_AARCH64
>       mc->default_cpu_type = ARM_CPU_TYPE_NAME("max");
> -#endif
> +#endif /* TARGET_AARCH64 */
> +#endif /* CONFIG_TCG */
>       mc->valid_cpu_types = valid_cpu_types;
>       mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
>       mc->kvm_type = virt_kvm_type;

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Zhang Chen]

On Thu, Apr 3, 2025 at 2:43 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 4/2/25 06:54, Zhang Chen wrote:
> > Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
> > is mistakenly set to the default AARCH64 target.
>
> This is the correct backward compatible setting.
> In essence, it means that you *must* supply a -cpu argument.
>
>

If the "-cpu" is required, the VM should not be started without this argument.
If yes, I will skip this patch and submit another one to make QEMU
refuse to start without this parameter.

Thanks
Chen

> r~
>
> >
> > Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> > ---
> >   hw/arm/virt.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index a96452f17a..63649e9543 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -3178,9 +3178,10 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
> >       mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
> >   #ifdef CONFIG_TCG
> >       mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
> > -#else
> > +#ifdef TARGET_AARCH64
> >       mc->default_cpu_type = ARM_CPU_TYPE_NAME("max");
> > -#endif
> > +#endif /* TARGET_AARCH64 */
> > +#endif /* CONFIG_TCG */
> >       mc->valid_cpu_types = valid_cpu_types;
> >       mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
> >       mc->kvm_type = virt_kvm_type;
>
>

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Zhang Chen]

On Thu, Apr 3, 2025 at 10:23 AM Zhang Chen <zhangckid@gmail.com> wrote:
>
> On Thu, Apr 3, 2025 at 2:43 AM Richard Henderson
> <richard.henderson@linaro.org> wrote:
> >
> > On 4/2/25 06:54, Zhang Chen wrote:
> > > Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
> > > is mistakenly set to the default AARCH64 target.
> >
> > This is the correct backward compatible setting.
> > In essence, it means that you *must* supply a -cpu argument.
> >
> >
>
> If the "-cpu" is required, the VM should not be started without this argument.
> If yes, I will skip this patch and submit another one to make QEMU
> refuse to start without this parameter.
>

Ping... and let me explain this status, it is not just for the default value.
1. The cpu type "cortex-a15" is not the correct backward compatible
setting for AARCH64 target.
The ARM cortex-a15 is a 32 bit CPU based on ARMv7-A architecture. It
can not boot for AARCH64 target.
For example, the Apple M silicon can not boot with the default -cpu value.

2. Most of QEMU docs does not said user *must* supply a -cpu argument.
https://www.qemu.org/docs/master/system/qemu-manpage.html

Thanks
Chen

> Thanks
> Chen
>
> > r~
> >
> > >
> > > Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> > > ---
> > >   hw/arm/virt.c | 5 +++--
> > >   1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > > index a96452f17a..63649e9543 100644
> > > --- a/hw/arm/virt.c
> > > +++ b/hw/arm/virt.c
> > > @@ -3178,9 +3178,10 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
> > >       mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
> > >   #ifdef CONFIG_TCG
> > >       mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
> > > -#else
> > > +#ifdef TARGET_AARCH64
> > >       mc->default_cpu_type = ARM_CPU_TYPE_NAME("max");
> > > -#endif
> > > +#endif /* TARGET_AARCH64 */
> > > +#endif /* CONFIG_TCG */
> > >       mc->valid_cpu_types = valid_cpu_types;
> > >       mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
> > >       mc->kvm_type = virt_kvm_type;
> >
> >

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Philippe Mathieu-Daudé]

On 24/4/25 10:56, Zhang Chen wrote:
> On Thu, Apr 3, 2025 at 10:23 AM Zhang Chen <zhangckid@gmail.com> wrote:
>>
>> On Thu, Apr 3, 2025 at 2:43 AM Richard Henderson
>> <richard.henderson@linaro.org> wrote:
>>>
>>> On 4/2/25 06:54, Zhang Chen wrote:
>>>> Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
>>>> is mistakenly set to the default AARCH64 target.
>>>
>>> This is the correct backward compatible setting.
>>> In essence, it means that you *must* supply a -cpu argument.
>>>
>>>
>>
>> If the "-cpu" is required, the VM should not be started without this argument.
>> If yes, I will skip this patch and submit another one to make QEMU
>> refuse to start without this parameter.
>>
> 
> Ping... and let me explain this status, it is not just for the default value.
> 1. The cpu type "cortex-a15" is not the correct backward compatible
> setting for AARCH64 target.

IIUC it was meant to be backward compatible for KVM (as in "not TCG"),
HVF was not a thing for ARM at this time.

> The ARM cortex-a15 is a 32 bit CPU based on ARMv7-A architecture. It
> can not boot for AARCH64 target.
> For example, the Apple M silicon can not boot with the default -cpu value.

A respin of this series might help you, I'll try to remember to Cc you:
https://lore.kernel.org/qemu-devel/b883f0ef-6131-4335-b273-90fd3d8cc5e4@linaro.org/

> 2. Most of QEMU docs does not said user *must* supply a -cpu argument.
> https://www.qemu.org/docs/master/system/qemu-manpage.html
> 
> Thanks
> Chen
> 
>> Thanks
>> Chen
>>
>>> r~
>>>
>>>>
>>>> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
>>>> ---
>>>>    hw/arm/virt.c | 5 +++--
>>>>    1 file changed, 3 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>>>> index a96452f17a..63649e9543 100644
>>>> --- a/hw/arm/virt.c
>>>> +++ b/hw/arm/virt.c
>>>> @@ -3178,9 +3178,10 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
>>>>        mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
>>>>    #ifdef CONFIG_TCG
>>>>        mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
>>>> -#else
>>>> +#ifdef TARGET_AARCH64
>>>>        mc->default_cpu_type = ARM_CPU_TYPE_NAME("max");
>>>> -#endif
>>>> +#endif /* TARGET_AARCH64 */
>>>> +#endif /* CONFIG_TCG */
>>>>        mc->valid_cpu_types = valid_cpu_types;
>>>>        mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
>>>>        mc->kvm_type = virt_kvm_type;
>>>
>>>
> 

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Zhang Chen]

On Thu, Apr 24, 2025 at 5:58 PM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> On 24/4/25 10:56, Zhang Chen wrote:
> > On Thu, Apr 3, 2025 at 10:23 AM Zhang Chen <zhangckid@gmail.com> wrote:
> >>
> >> On Thu, Apr 3, 2025 at 2:43 AM Richard Henderson
> >> <richard.henderson@linaro.org> wrote:
> >>>
> >>> On 4/2/25 06:54, Zhang Chen wrote:
> >>>> Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
> >>>> is mistakenly set to the default AARCH64 target.
> >>>
> >>> This is the correct backward compatible setting.
> >>> In essence, it means that you *must* supply a -cpu argument.
> >>>
> >>>
> >>
> >> If the "-cpu" is required, the VM should not be started without this argument.
> >> If yes, I will skip this patch and submit another one to make QEMU
> >> refuse to start without this parameter.
> >>
> >
> > Ping... and let me explain this status, it is not just for the default value.
> > 1. The cpu type "cortex-a15" is not the correct backward compatible
> > setting for AARCH64 target.
>
> IIUC it was meant to be backward compatible for KVM (as in "not TCG"),
> HVF was not a thing for ARM at this time.
>
> > The ARM cortex-a15 is a 32 bit CPU based on ARMv7-A architecture. It
> > can not boot for AARCH64 target.
> > For example, the Apple M silicon can not boot with the default -cpu value.
>
> A respin of this series might help you, I'll try to remember to Cc you:
> https://lore.kernel.org/qemu-devel/b883f0ef-6131-4335-b273-90fd3d8cc5e4@linaro.org/
>

Thanks Philippe, your patch fix the same issue and looks good for me.
Let's drop this patch.

Thanks
Chen



> > 2. Most of QEMU docs does not said user *must* supply a -cpu argument.
> > https://www.qemu.org/docs/master/system/qemu-manpage.html
> >
> > Thanks
> > Chen
> >
> >> Thanks
> >> Chen
> >>
> >>> r~
> >>>
> >>>>
> >>>> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> >>>> ---
> >>>>    hw/arm/virt.c | 5 +++--
> >>>>    1 file changed, 3 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> >>>> index a96452f17a..63649e9543 100644
> >>>> --- a/hw/arm/virt.c
> >>>> +++ b/hw/arm/virt.c
> >>>> @@ -3178,9 +3178,10 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
> >>>>        mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
> >>>>    #ifdef CONFIG_TCG
> >>>>        mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
> >>>> -#else
> >>>> +#ifdef TARGET_AARCH64
> >>>>        mc->default_cpu_type = ARM_CPU_TYPE_NAME("max");
> >>>> -#endif
> >>>> +#endif /* TARGET_AARCH64 */
> >>>> +#endif /* CONFIG_TCG */
> >>>>        mc->valid_cpu_types = valid_cpu_types;
> >>>>        mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
> >>>>        mc->kvm_type = virt_kvm_type;
> >>>
> >>>
> >
>

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Peter Maydell]

On Thu, 24 Apr 2025 at 09:57, Zhang Chen <zhangckid@gmail.com> wrote:
>
> On Thu, Apr 3, 2025 at 10:23 AM Zhang Chen <zhangckid@gmail.com> wrote:
> >
> > On Thu, Apr 3, 2025 at 2:43 AM Richard Henderson
> > <richard.henderson@linaro.org> wrote:
> > >
> > > On 4/2/25 06:54, Zhang Chen wrote:
> > > > Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
> > > > is mistakenly set to the default AARCH64 target.
> > >
> > > This is the correct backward compatible setting.
> > > In essence, it means that you *must* supply a -cpu argument.
> > >
> > >
> >
> > If the "-cpu" is required, the VM should not be started without this argument.
> > If yes, I will skip this patch and submit another one to make QEMU
> > refuse to start without this parameter.
> >
>
> Ping... and let me explain this status, it is not just for the default value.
> 1. The cpu type "cortex-a15" is not the correct backward compatible
> setting for AARCH64 target.
> The ARM cortex-a15 is a 32 bit CPU based on ARMv7-A architecture. It
> can not boot for AARCH64 target.
> For example, the Apple M silicon can not boot with the default -cpu value.

'qemu-system-aarch64' doesn't mean "I want an AArch64 CPU", it
just means that you can select AArch64 machines and CPUs. Almost
all command lines that work with qemu-system-arm also do the same
thing if run with qemu-system-aarch64. So in this case,
"qemu-system-aarch64 -M virt" does the same as "qemu-system-arm -M virt",
including the CPU type selected.

The Cortex-A15 is now very rarely what anybody wants, but we
keep it this way to avoid breaking existing users' command lines.
(It works fine if you pass it a 32-bit guest kernel.)

thanks
-- PMM

Re: [PATCH] hw/arm/virt.c: Fix wrong default cpu type in AARCH64

[Zhang Chen]

On Mon, Apr 28, 2025 at 8:47 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Thu, 24 Apr 2025 at 09:57, Zhang Chen <zhangckid@gmail.com> wrote:
> >
> > On Thu, Apr 3, 2025 at 10:23 AM Zhang Chen <zhangckid@gmail.com> wrote:
> > >
> > > On Thu, Apr 3, 2025 at 2:43 AM Richard Henderson
> > > <richard.henderson@linaro.org> wrote:
> > > >
> > > > On 4/2/25 06:54, Zhang Chen wrote:
> > > > > Because of the CONFIG_TCG auto enabled, the cpu type "cortex-a15"
> > > > > is mistakenly set to the default AARCH64 target.
> > > >
> > > > This is the correct backward compatible setting.
> > > > In essence, it means that you *must* supply a -cpu argument.
> > > >
> > > >
> > >
> > > If the "-cpu" is required, the VM should not be started without this argument.
> > > If yes, I will skip this patch and submit another one to make QEMU
> > > refuse to start without this parameter.
> > >
> >
> > Ping... and let me explain this status, it is not just for the default value.
> > 1. The cpu type "cortex-a15" is not the correct backward compatible
> > setting for AARCH64 target.
> > The ARM cortex-a15 is a 32 bit CPU based on ARMv7-A architecture. It
> > can not boot for AARCH64 target.
> > For example, the Apple M silicon can not boot with the default -cpu value.
>
> 'qemu-system-aarch64' doesn't mean "I want an AArch64 CPU", it
> just means that you can select AArch64 machines and CPUs. Almost
> all command lines that work with qemu-system-arm also do the same
> thing if run with qemu-system-aarch64. So in this case,
> "qemu-system-aarch64 -M virt" does the same as "qemu-system-arm -M virt",
> including the CPU type selected.
>
> The Cortex-A15 is now very rarely what anybody wants, but we
> keep it this way to avoid breaking existing users' command lines.
> (It works fine if you pass it a 32-bit guest kernel.)

Thanks Peter for the detailed explanation. I got the background of the AArch64.
I'm just interested in Apple M silicon with HVF recently.

Thanks
Chen

>
> thanks
> -- PMM