From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 13 Jan 2016 11:22:19 +0000 Subject: [PATCH v2 3/3] iommu/io-pgtable: Avoid redundant TLB syncs In-Reply-To: <56963297.7090605@arm.com> References: <20160112182754.GC22186@arm.com> <56963297.7090605@arm.com> Message-ID: <5696336B.6080003@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 13/01/16 11:18, Robin Murphy wrote: > On 12/01/16 18:27, 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 >>> --- >>> 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? > > Ooh, tlb_flush_pending is a much nicer name indeed. It's almost as if I Or tlb_sync_pending, even. Bah, mornings... > threw this together in a pre-holiday rush and put very little thought > into it... > > I've fixed it up locally, but I'll save the repost until after -rc1, > especially in case Yong has any further comments in the meantime. > > Thanks, > Robin. > > _______________________________________________ > iommu mailing list > iommu at lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu >