[v8,03/19] target/riscv/cpu.c: set satp_max_supported in cpu_riscv_set_satp()

The setter() for the boolean attributes that set satp_mode (sv32, sv39,
sv48, sv57, sv64) considers that the CPU will always do a
set_satp_mode_max_supported() during cpu_init().

This is not the case for the KVM 'host' CPU, and we'll add another CPU
that won't set satp_mode_max() during cpu_init(). Users should be able
to set a max_support in these circunstances.

Allow cpu_riscv_set_satp() to set satp_mode_max_supported if the CPU
didn't set one prior.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

On Wed, Nov 01, 2023 at 05:41:48PM -0300, Daniel Henrique Barboza wrote:
> The setter() for the boolean attributes that set satp_mode (sv32, sv39,
> sv48, sv57, sv64) considers that the CPU will always do a
> set_satp_mode_max_supported() during cpu_init().
> 
> This is not the case for the KVM 'host' CPU, and we'll add another CPU
> that won't set satp_mode_max() during cpu_init(). Users should be able
> to set a max_support in these circunstances.
> 
> Allow cpu_riscv_set_satp() to set satp_mode_max_supported if the CPU
> didn't set one prior.
> 
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 822970345c..9f6837ecb7 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1100,6 +1100,7 @@ static void cpu_riscv_get_satp(Object *obj, Visitor *v, const char *name,
>  static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
>                                 void *opaque, Error **errp)
>  {
> +    RISCVCPU *cpu = RISCV_CPU(obj);
>      RISCVSATPMap *satp_map = opaque;
>      uint8_t satp = satp_mode_from_str(name);
>      bool value;
> @@ -1108,6 +1109,16 @@ static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
>          return;
>      }
>  
> +    /*
> +     * Allow users to set satp max supported if the CPU didn't
> +     * set any during cpu_init(). First value set to 'true'
> +     * in this case is assumed to be the max supported for
> +     * the CPU.

Hmm, doesn't that mean if a user does

 -cpu rv64,sv39=true,sv48=true

then the max is set to sv39 instead of sv48?

I made a mistake in my last review by stating we shouldn't set the max
supported satp for rv64i to the maximum satp that TCG supports. I forgot
how all of it worked. Setting the _supported_ modes to the maximum that
TCG supports makes sense as long as we don't default to any of them for
rv64i. So, I think we should return the set_satp_mode_max_supported() to
rv64i's definition (passing VM_1_10_SV57 or maybe even VM_1_10_SV64) and
then change set_satp_mode_default_map() to error out for rv64i (or maybe
for all "bare" type cpus).

> +     */
> +    if (value && cpu->cfg.satp_mode.supported == 0) {
> +        set_satp_mode_max_supported(cpu, satp);
> +    }
> +
>      satp_map->map = deposit32(satp_map->map, satp, 1, value);
>      satp_map->init |= 1 << satp;
>  }
> -- 
> 2.41.0
>

Thanks,
drew

On 11/2/23 06:24, Andrew Jones wrote:
> On Wed, Nov 01, 2023 at 05:41:48PM -0300, Daniel Henrique Barboza wrote:
>> The setter() for the boolean attributes that set satp_mode (sv32, sv39,
>> sv48, sv57, sv64) considers that the CPU will always do a
>> set_satp_mode_max_supported() during cpu_init().
>>
>> This is not the case for the KVM 'host' CPU, and we'll add another CPU
>> that won't set satp_mode_max() during cpu_init(). Users should be able
>> to set a max_support in these circunstances.
>>
>> Allow cpu_riscv_set_satp() to set satp_mode_max_supported if the CPU
>> didn't set one prior.
>>
>> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
>> ---
>>   target/riscv/cpu.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
>> index 822970345c..9f6837ecb7 100644
>> --- a/target/riscv/cpu.c
>> +++ b/target/riscv/cpu.c
>> @@ -1100,6 +1100,7 @@ static void cpu_riscv_get_satp(Object *obj, Visitor *v, const char *name,
>>   static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
>>                                  void *opaque, Error **errp)
>>   {
>> +    RISCVCPU *cpu = RISCV_CPU(obj);
>>       RISCVSATPMap *satp_map = opaque;
>>       uint8_t satp = satp_mode_from_str(name);
>>       bool value;
>> @@ -1108,6 +1109,16 @@ static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
>>           return;
>>       }
>>   
>> +    /*
>> +     * Allow users to set satp max supported if the CPU didn't
>> +     * set any during cpu_init(). First value set to 'true'
>> +     * in this case is assumed to be the max supported for
>> +     * the CPU.
> 
> Hmm, doesn't that mean if a user does
> 
>   -cpu rv64,sv39=true,sv48=true
> 
> then the max is set to sv39 instead of sv48?
> 
> I made a mistake in my last review by stating we shouldn't set the max
> supported satp for rv64i to the maximum satp that TCG supports. I forgot
> how all of it worked. Setting the _supported_ modes to the maximum that
> TCG supports makes sense as long as we don't default to any of them for
> rv64i. So, I think we should return the set_satp_mode_max_supported() to
> rv64i's definition (passing VM_1_10_SV57 or maybe even VM_1_10_SV64) and
> then change set_satp_mode_default_map() to error out for rv64i (or maybe
> for all "bare" type cpus).

Ok, then let's set max supported mode to SV64 (the maximum we allow).

Then we don't need to do anything else - setting a max supported value will allow
TCG to handle it accordingly with OpenSBI and the kernel, and a suitable satp_mode
will be picked by them. We can leave finalize() untouched.

I'll make a note in cpu_init() to remind ourselves that we're not setting a default
satp_mode value, but a *limit* for the satp_mode value the CPU can handle. This can be
done in the 'rv64i' patch.


Thanks,


Daniel




> 
>> +     */
>> +    if (value && cpu->cfg.satp_mode.supported == 0) {
>> +        set_satp_mode_max_supported(cpu, satp);
>> +    }
>> +
>>       satp_map->map = deposit32(satp_map->map, satp, 1, value);
>>       satp_map->init |= 1 << satp;
>>   }
>> -- 
>> 2.41.0
>>
> 
> Thanks,
> drew

On Thu, Nov 02, 2023 at 09:53:50AM -0300, Daniel Henrique Barboza wrote:
> 
> 
> On 11/2/23 06:24, Andrew Jones wrote:
> > On Wed, Nov 01, 2023 at 05:41:48PM -0300, Daniel Henrique Barboza wrote:
> > > The setter() for the boolean attributes that set satp_mode (sv32, sv39,
> > > sv48, sv57, sv64) considers that the CPU will always do a
> > > set_satp_mode_max_supported() during cpu_init().
> > > 
> > > This is not the case for the KVM 'host' CPU, and we'll add another CPU
> > > that won't set satp_mode_max() during cpu_init(). Users should be able
> > > to set a max_support in these circunstances.
> > > 
> > > Allow cpu_riscv_set_satp() to set satp_mode_max_supported if the CPU
> > > didn't set one prior.
> > > 
> > > Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> > > ---
> > >   target/riscv/cpu.c | 11 +++++++++++
> > >   1 file changed, 11 insertions(+)
> > > 
> > > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> > > index 822970345c..9f6837ecb7 100644
> > > --- a/target/riscv/cpu.c
> > > +++ b/target/riscv/cpu.c
> > > @@ -1100,6 +1100,7 @@ static void cpu_riscv_get_satp(Object *obj, Visitor *v, const char *name,
> > >   static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
> > >                                  void *opaque, Error **errp)
> > >   {
> > > +    RISCVCPU *cpu = RISCV_CPU(obj);
> > >       RISCVSATPMap *satp_map = opaque;
> > >       uint8_t satp = satp_mode_from_str(name);
> > >       bool value;
> > > @@ -1108,6 +1109,16 @@ static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
> > >           return;
> > >       }
> > > +    /*
> > > +     * Allow users to set satp max supported if the CPU didn't
> > > +     * set any during cpu_init(). First value set to 'true'
> > > +     * in this case is assumed to be the max supported for
> > > +     * the CPU.
> > 
> > Hmm, doesn't that mean if a user does
> > 
> >   -cpu rv64,sv39=true,sv48=true
> > 
> > then the max is set to sv39 instead of sv48?
> > 
> > I made a mistake in my last review by stating we shouldn't set the max
> > supported satp for rv64i to the maximum satp that TCG supports. I forgot
> > how all of it worked. Setting the _supported_ modes to the maximum that
> > TCG supports makes sense as long as we don't default to any of them for
> > rv64i. So, I think we should return the set_satp_mode_max_supported() to
> > rv64i's definition (passing VM_1_10_SV57 or maybe even VM_1_10_SV64) and
> > then change set_satp_mode_default_map() to error out for rv64i (or maybe
> > for all "bare" type cpus).
> 
> Ok, then let's set max supported mode to SV64 (the maximum we allow).
> 
> Then we don't need to do anything else - setting a max supported value will allow
> TCG to handle it accordingly with OpenSBI and the kernel, and a suitable satp_mode
> will be picked by them. We can leave finalize() untouched.
> 
> I'll make a note in cpu_init() to remind ourselves that we're not setting a default
> satp_mode value, but a *limit* for the satp_mode value the CPU can handle.

It's both. It's the limit and, in the absence of user input, its used as
the default. Setting the limit is fine for a no-default cpu type, but
allowing it to become the default is not. We need to also modify
set_satp_mode_default_map() to only do what it does for non no-default
cpus types.

Thanks,
drew