Re: [PATCH v15 04/23] cpu: Move synchronize_from_tb() to tcg_ops

[Claudio Fontana]

On 2/3/21 1:31 PM, Claudio Fontana wrote:
> On 2/3/21 11:11 AM, Alex Bennée wrote:
>>
>> Claudio Fontana <cfontana@suse.de> writes:
>>
>>> From: Eduardo Habkost <ehabkost@redhat.com>
>>>
>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>>
>>> [claudio: wrapped target code in CONFIG_TCG]
>>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>>> ---
>>>  include/hw/core/cpu.h     | 20 +++++++++++---------
>>>  accel/tcg/cpu-exec.c      |  4 ++--
>>>  target/arm/cpu.c          |  4 +++-
>>>  target/avr/cpu.c          |  2 +-
>>>  target/hppa/cpu.c         |  2 +-
>>>  target/i386/tcg/tcg-cpu.c |  2 +-
>>>  target/microblaze/cpu.c   |  2 +-
>>>  target/mips/cpu.c         |  4 +++-
>>>  target/riscv/cpu.c        |  2 +-
>>>  target/rx/cpu.c           |  2 +-
>>>  target/sh4/cpu.c          |  2 +-
>>>  target/sparc/cpu.c        |  2 +-
>>>  target/tricore/cpu.c      |  2 +-
>>>  13 files changed, 28 insertions(+), 22 deletions(-)
>>>
>>> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
>>> index d0b17dcc4c..b9803885e5 100644
>>> --- a/include/hw/core/cpu.h
>>> +++ b/include/hw/core/cpu.h
>>> @@ -86,6 +86,17 @@ typedef struct TcgCpuOperations {
>>>       * Called when the first CPU is realized.
>>>       */
>>>      void (*initialize)(void);
>>> +    /**
>>> +     * @synchronize_from_tb: Synchronize state from a TCG #TranslationBlock
>>> +     *
>>> +     * This is called when we abandon execution of a TB before
>>> +     * starting it, and must set all parts of the CPU state which
>>> +     * the previous TB in the chain may not have updated. This
>>> +     * will need to do more. If this hook is not implemented then
>>> +     * the default is to call @set_pc(tb->pc).
>>> +     */
>>> +    void (*synchronize_from_tb)(CPUState *cpu,
>>> +                                const struct TranslationBlock *tb);
>>
>> Did you miss my comment last time or just not think it flowed better?
>>
>>   ...TB in the chain may not have updated. By default when no hook is
>>   defined a call is made to @set_pc(tb->pc). If more state needs to be
>>   restored the front-end must provide a hook function and restore all the
>>   state there.
>>
>> Either way:
>>
>> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>>
> 
> Hi Alex, sorry for missing this change, can add it for the next respin,
> 
> and thanks for looking at this,
> 
> Ciao,
> 
> Claudio

    /**                                                                         
                                                            
     * @synchronize_from_tb: Synchronize state from a TCG #TranslationBlock     
                                                            
     *                                                                          
                                                            
     * This is called when we abandon execution of a TB before starting it,     
                                                            
     * and must set all parts of the CPU state which the previous TB in the     
                                                            
     * chain may not have updated.                                              
                                                            
     * By default, when this is NULL, a call is made to @set_pc(tb->pc).        
                                                            
     *                                                                          
                                                            
     * If more state needs to be restored, the target must implement a          
                                                            
     * function to restore all the state, and register it here.                 
                                                            
     */


I changed the wording a bit, because to me it is easier to think about "target" 
than about "front-end", but maybe I am missing something.
I am also not in love with the term hook, we are trying to end up with a proper 
interface, as we complete this series,
a nice struct that the target can provide with all the functions necessary to 
implement the TCG operations.

Let me know if this requires additional revision,

Ciao,

CLaudio