iommu/iova: Add flush counters to Flush-Queue implementation

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There are two counters:

	* fq_flush_start_cnt  - Increased when a TLB flush
	                        is started.

	* fq_flush_finish_cnt - Increased when a TLB flush
				is finished.

The fq_flush_start_cnt is assigned to every Flush-Queue
entry on its creation. When freeing entries from the
Flush-Queue, the value in the entry is compared to the
fq_flush_finish_cnt. The entry can only be freed when its
value is less than the value of fq_flush_finish_cnt.

The reason for these counters it to take advantage of IOMMU
TLB flushes that happened on other CPUs. These already
flushed the TLB for Flush-Queue entries on other CPUs so
that they can already be freed without flushing the TLB
again.

This makes it less likely that the Flush-Queue is full and
saves IOMMU TLB flushes.

Signed-off-by: Joerg Roedel <jroedel@suse.de>

...

This commit is contained in:

Joerg Roedel 2017-08-10 16:14:59 +02:00

parent 1928210107

commit fb418dab8a

2 changed files with 32 additions and 3 deletions

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29

drivers/iommu/iova.c

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8

include/linux/iova.h

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