Re: [PATCH v2 09/11] xen/riscv: introduce p2m_gpa_bits

[Jan Beulich <jbeulich@xxxxxxxx>]

On 01.04.2026 15:50, Oleksii Kurochko wrote:
> On 4/1/26 8:07 AM, Jan Beulich wrote:
>>>>> @@ -191,8 +209,13 @@ static void __init gstage_mode_detect(void)
>>>>>    
>>>>>    void __init guest_mm_init(void)
>>>>>    {
>>>>> +    unsigned int gpa_bits;
>>>>> +    unsigned int paging_levels = default_gstage_mode.paging_levels;
>>>> Deriving a global from a default, when ...

This earlier comment may have been placed a little unhelpfully. The global
talked about is p2m_gpa_bits. IOW ...

>>>>>        gstage_mode_detect();
>>>>>    
>>>>> +    ASSERT(default_gstage_mode.paging_levels <= 
>>>>> max_gstage_mode.paging_levels);
>>>> ... the default isn't the maximum possible, isn't going to fly.
>>> I didn't get you here.
>>>
>>> If we want Xen uses Sv39 for G-stage, we want to limit guest's 56-bit
>>> GPA to 39-bit GPA, but not the maximum supported by h/w mode for G-stage
>>> mode.
>> I can only repeat what I thought I had got across already on an earlier
>> series of yours: What mode a guest is going to use is going to be a guest
>> property. The default mode therefore isn't the only mode that may be used
>> at runtime.
> 
> I remember that, but i don't really understand what is wrong now with 
> the ASSERT(). It should be changed or dropped at all when this property 
> you are talking about will be introduced.

... the comment wasn't about the assertion itself, but the mere existence
of default_gstage_mode. Imo you really don't want to redo this later, but
maintain per-guest settings per guest right away, even if for the time
being all guests may end up with identical settings.

Jan