From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 13 Jan 2016 11:18:47 +0000 Subject: [PATCH v2 3/3] iommu/io-pgtable: Avoid redundant TLB syncs In-Reply-To: <20160112182754.GC22186@arm.com> References: <20160112182754.GC22186@arm.com> Message-ID: <56963297.7090605@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 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.