diff options
Diffstat (limited to 'drivers/iommu/arm-smmu-v3.c')
| -rw-r--r-- | drivers/iommu/arm-smmu-v3.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index b36a99971401..3402b1bc8e94 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -1286,6 +1286,22 @@ static void arm_smmu_cmdq_write_entries(struct arm_smmu_cmdq *cmdq, u64 *cmds, } } +/* + * This is the actual insertion function, and provides the following + * ordering guarantees to callers: + * + * - There is a dma_wmb() before publishing any commands to the queue. + * This can be relied upon to order prior writes to data structures + * in memory (such as a CD or an STE) before the command. + * + * - On completion of a CMD_SYNC, there is a control dependency. + * This can be relied upon to order subsequent writes to memory (e.g. + * freeing an IOVA) after completion of the CMD_SYNC. + * + * - Command insertion is totally ordered, so if two CPUs each race to + * insert their own list of commands then all of the commands from one + * CPU will appear before any of the commands from the other CPU. + */ static int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu, u64 *cmds, int n, bool sync) { |