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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 <laurent.pinchart@ideasonboard.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Robin Murphy 2016-01-26 17:13:15 +00:00 committed by Will Deacon
parent 507e4c9d19
commit 88492a4700
1 changed files with 8 additions and 1 deletions
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9
drivers/iommu/io-pgtable.h
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@ -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;
}
}
/**