Re: [RFC PATCH] Added the logic to decode 32 bit ldr/str post-indexing instructions

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 22 Nov 2021, Julien Grall wrote:
> On Mon, 22 Nov 2021 at 19:59, Stefano Stabellini <sstabellini@xxxxxxxxxx> 
> wrote:
> >
> > On Mon, 22 Nov 2021, Ayan Kumar Halder wrote:
> > > Stefano > It doesn't look like we are setting dabt->write anywhere.
> > >
> > > Ayan > Yes, this is a miss. Depending on the opc, this should be upadeted
> > > accordingly in decode_64bit_loadstore_postindexing().
> > >
> > > Stefano > Also, is info.gpa in try_handle_mmio already updated in the
> > > pre-index
> > > case? If not, do we need to apply the offset manually here?
> > >
> > > Ayan > Sorry, I did not understand you. This patch is only related to the 
> > > post
> > > indexing ldr/str issue. Why do we need to check for pre-indexing ?
> >
> > I thought you were trying to handle both post-indexing and pre-indexing.
> > It is OK if you intend to only handle post-indexing but considering that
> > most of the code is shared between the two, we might as well also make
> > pre-indexing work (unless it turns out it is more difficult).
> 
> Wouldn't this effectively be dead code?
> 
> >
> > In the pre-indexing case, I would imagine we need to update the base
> > address before taking any other actions.
> 
> >From my understanding, this would have already been performed by the
> HW when the syndrome is valid. This may also be the case for
> the non-valid case, but I haven't checked the Arm Arm.

It is not clear to me either, that's why I wrote "I would imagine"... I
was guessing that it is not done by the HW in the non-valid case but I
don't know.

Of course, if it is already done by the HW, that's all the better: no
need for us to do anything.