From 88492a4700360a086e55d8874ad786105a5e8b0f Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Tue, 26 Jan 2016 17:13:15 +0000 Subject: [PATCH] iommu/io-pgtable: Avoid redundant TLB syncs 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. Reviewed-by: Laurent Pinchart Signed-off-by: Robin Murphy Signed-off-by: Will Deacon --- 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 95c5565b6669..4faee7d23ee9 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. + * @tlb_sync_pending: Private flag for optimising out redundant syncs. * @cfg: A copy of the page table configuration. * @ops: The page table operations in use for this set of page tables. */ struct io_pgtable { enum io_pgtable_fmt fmt; void *cookie; + bool tlb_sync_pending; struct io_pgtable_cfg cfg; struct io_pgtable_ops ops; }; @@ -147,17 +149,22 @@ struct io_pgtable { static inline void io_pgtable_tlb_flush_all(struct io_pgtable *iop) { iop->cfg.tlb->tlb_flush_all(iop->cookie); + iop->tlb_sync_pending = true; } static inline void io_pgtable_tlb_add_flush(struct io_pgtable *iop, unsigned long iova, size_t size, size_t granule, bool leaf) { iop->cfg.tlb->tlb_add_flush(iova, size, granule, leaf, iop->cookie); + iop->tlb_sync_pending = true; } static inline void io_pgtable_tlb_sync(struct io_pgtable *iop) { - iop->cfg.tlb->tlb_sync(iop->cookie); + if (iop->tlb_sync_pending) { + iop->cfg.tlb->tlb_sync(iop->cookie); + iop->tlb_sync_pending = false; + } } /** -- 2.20.1