Re: [PATCH v3] hw/arm/smmuv3: Add GBPA register

[Mostafa Saleh <smostafa@google.com>]

On Fri, Feb 10, 2023 at 04:11:37PM +0000, Peter Maydell wrote:
> 
> I think we should check the whole register against its reset value,
> not just the ABORT bit. Otherwise if the guest writes the other fields
> to non default values we won't migrate them. That doesn't change the
> device behaviour now but it will have the weird effect that the guest
> could write the register and then after a migration find it reading
> back as a different value. Plus if in future we implement actual
> functionality for any of the other fields then we'll want to know
> what their true values written by the guest are.
> 
> Linux never changes any fields except ABORT so for the most interesting
> guest it won't make a difference right now.

I agree, I was trying to achieve maximum backward compatibility as we
don’t care about other fields, but this can be weird for forward
migration, if the register is not fully migrated.
And if SW touches this register it would probably want to configure the
ABORT at some point, so it won’t help much for backward migration.

I will update this in v4.

Thanks,
Mostafa