Re: [PATCH v3] memory: Optimize replay of guest mapping

[Peter Maydell]

On Wed, 19 Apr 2023 at 03:38, Duan, Zhenzhong <zhenzhong.duan@intel.com> wrote:

> >> The documentation for the replay method of IOMMUMemoryRegionClass
> >> says:
> >>      * The default implementation of memory_region_iommu_replay() is to
> >>      * call the IOMMU translate method for every page in the address space
> >>      * with flag == IOMMU_NONE and then call the notifier if translate
> >>      * returns a valid mapping. If this method is implemented then it
> >>      * overrides the default behaviour, and must provide the full semantics
> >>      * of memory_region_iommu_replay(), by calling @notifier for every
> >>      * translation present in the IOMMU.
> >>
> >> This commit changes the default implementation so it's no longer doing
> >> this for every page in the address space. If the change is correct, we
> >> should update the doc comment too.
> >>
> >> Oddly, the doc comment for memory_region_iommu_replay() itself doesn't
> >> very clearly state what its semantics are; it could probably be
> >> improved.
> >>
> >> Anyway, this change is OK for the TCG use of iommu notifiers, because
> >> that doesn't care about replay.
> >
> >Since the notifier contains the range information I'd say the change 
> >shouldn't
> >affect any caller but only a pure performance difference.  Indeed it'll be 
> >nicer
> >the documentation can be updated too.  Thanks,

> Thanks Peter Maydell and Peter Xu's comments, will add doc update.
> May I ask if it's preferred to add doc update to this patch or a separate 
> patch?

I suggest doing it in this same patch.

thanks
-- PMM