Re: [PATCH] AMD/IOMMU: drop remaining guest-IOMMU bits too

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Mar 20, 2024 at 03:51:55PM +0100, Jan Beulich wrote:
> On 20.03.2024 15:06, Roger Pau Monné wrote:
> > On Wed, Mar 20, 2024 at 11:58:50AM +0100, Jan Beulich wrote:
> >> On 20.03.2024 11:46, Roger Pau Monné wrote:
> >>> On Tue, Mar 19, 2024 at 02:28:12PM +0100, Jan Beulich wrote:
> >>>> With a02174c6c885 ("amd/iommu: clean up unused guest iommu related
> >>>> functions") having removed the sole place where d->g_iommu would be set
> >>>> to non-NULL, guest_iommu_add_ppr_log() will unconditionally bail the
> >>>> latest from its 2nd if(). With it dropped, all other stuff in the file
> >>>> is unused, too. Delete iommu_guest.c altogether.
> >>>>
> >>>> Further delete struct guest{_buffer,_dev_table,_iommu{,_msi}} as well as
> >>>> struct mmio_reg for being unused with the unused g_iommu also dropped
> >>>> from struct arch_iommu.
> >>>>
> >>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > 
> > Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> Thanks.
> 
> >>>> ---
> >>>> I wasn't sure how far to further go with removing the body of
> >>>> parse_ppr_log_entry(), or perhaps even the entire function, and then
> >>>> further up to all PPR logging code. Hence why for now I've merely
> >>>> commented out the function call into the file being deleted (which of
> >>>> course Misra isn't going to like). Thoughts / suggestions?
> >>>>
> >>>> I further wonder whether set_iommu_guest_translation_control() should
> >>>> have been invoked independent of guest-IOMMU actually being enabled. IOW
> >>>> that may want purging, too. Along these lines iommuv2_enabled may also
> >>>> want dropping, for not having any consumer left. Much like has_viommu()
> >>>> and then also {XEN_,}X86_EMU_IOMMU, i.e. going as far as affecting the
> >>>> public interface.
> > 
> > I would drop it all.  The public interface part is not stable anyway,
> > as it's a domctl, but I would be fine if you want to keep the X86_EMU_IOMMU.
> 
> By "all" you also mean the PPR logging code? That's where I felt I might
> be going too far ...

It's up to you.  I've taken a look, and the PPR logging code seems to
be tied to guest IOMMU also?

Since PPR could be used for other purposes it's likely fine to leave
it in, albeit I won't oppose if you want to remove it (maybe there's
some purpose I'm missing).

Thanks, Roger.