v2 -> v3:
Although I have no data to show how many performance will be impacted
because of arm_smmu_cmdq_build_cmd is protected by spinlock. But it's
clear that the performance is bound to drop, a memset operation and
a complicate switch..case in the function arm_smmu_cmdq_build_cmd.
v1 -> v2:
1. move the call to arm_smmu_cmdq_build_cmd into the critical section,
and keep itself unchange.
2. Although patch2 can make sure no two CMD_SYNCs will be adjacent,
but patch1 is still needed, see below:
cpu0 cpu1 cpu2
msidata=0
msidata=1
insert cmd1
insert a TLBI command
insert cmd0
smmu execute cmd1
smmu execute TLBI
smmu execute cmd0
poll timeout, because msidata=1 is overridden by
cmd0, that means VAL=0, sync_idx=1.
Zhen Lei (2):
iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout
iommu/arm-smmu-v3: avoid redundant CMD_SYNCs if possible
drivers/iommu/arm-smmu-v3.c | 30 +++++++++++++++++++++++++-----
1 file changed, 25 insertions(+), 5 deletions(-)
--
1.8.3
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