Re: [PATCH v2 4/6] arm/mpu: Destroy an existing entry in Xen MPU memory mapping table

[Orzel, Michal]

On 11/07/2025 08:04, Hari Limaye wrote:
> Hi Michal,
> 
> Thank you for reviewing the patch.
> 
>  
> 
>> > +    /* Zeroing the region will also zero the region enable */
> 
>> > +    memset(&xen_mpumap[index], 0, sizeof(pr_t));
> 
>> Is it ok that for a fast case (i.e. 0-31) our representation of prbar/prlar 
>> will
> 
>> be different from the HW i.e. xen_mpumap[index] is 0 vs only .en bit of prlar
> 
>> being 0 in HW?
> 
>  
> 
> I think this should not matter - there is nothing reading registers directly 
> and
> 
> all the decisions are taken looking into xen_mpumap.
> 
>  
> 
> However, if you would prefer, we could alter the logic here to only clear the 
> .en
> 
> bit in xen_mpumap[index] in the fast case, so that things remain consistent?
> Alternatively we could always directly zero the entirety of the registers, but
> then we would remove the use of the fast case entirely.
I don't have a strong preference here. I think we can keep your current 
solution.

~Michal