Subject: [PATCH v2 3/3] iommu/io-pgtable: Avoid redundant TLB syncs

From: [email-masked] (Laurent Pinchart)
Date: Sat, 16 Jan 2016 01:26:37 +0200

Hi Robin,

Thank you for the patch.

On Tuesday 12 January 2016 18:27:55 Will Deacon wrote:
> On Thu, Dec 17, 2015 at 08:50:59PM +0000, Robin Murphy wrote:
> > In certain unmapping situations it is quite possible to end up issuing
> > back-to-back TLB synchronisations, which at best is a waste of time and
> > effort, and at worst causes some hardware to get rather confused. Whilst
> > the pagetable implementations, or the IOMMU drivers, or both, could keep
> > track of things to avoid this happening, it seems to make the most sense
> > to prevent code duplication and add some simple state tracking in the
> > common interface between the two.
> > 
> > Signed-off-by: Robin Murphy <[email-masked]>
> > ---
> > 
> >  drivers/iommu/io-pgtable.h | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/io-pgtable.h b/drivers/iommu/io-pgtable.h
> > index 95c5565..d06219b 100644
> > --- a/drivers/iommu/io-pgtable.h
> > +++ b/drivers/iommu/io-pgtable.h
> > @@ -132,12 +132,14 @@ void free_io_pgtable_ops(struct io_pgtable_ops
> > *ops);
> > 
> >   * @fmt:    The page table format.
> >   * @cookie: An opaque token provided by the IOMMU driver and passed back
> >   to
> >   *          any callback routines.
> > 
> > + * @sync_flag: Private flag for optimising out redundant syncs.
> 
> It makes sense to factor this out like you're proposing, but maybe we
> can think of a better name? How about "tlb_sync_pending", to follow
> "tlb_flush_pending" in the core code?

With tlb_sync_pending,

Reviewed-by: Laurent Pinchart <[email-masked]>

-- 
Regards,

Laurent Pinchart