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| author | Zhen Lei <thunder.leizhen@huawei.com> | 2018-08-19 09:51:10 +0200 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2018-10-01 14:01:30 +0200 |
| commit | 0f02477d16980938a84aba8688a4e3a303306116 (patch) | |
| tree | b56b2730a54ece3940ce9a735a62c9730d63c7bf /drivers/iommu | |
| parent | iommu/io-pgtable-arm: Fix race handling in split_blk_unmap() (diff) | |
| download | linux-0f02477d16980938a84aba8688a4e3a303306116.tar.xz linux-0f02477d16980938a84aba8688a4e3a303306116.zip | |
iommu/arm-smmu-v3: Fix unexpected CMD_SYNC timeout
The condition break condition of:
(int)(VAL - sync_idx) >= 0
in the __arm_smmu_sync_poll_msi() polling loop requires that sync_idx
must be increased monotonically according to the sequence of the CMDs in
the cmdq.
However, since the msidata is populated using atomic_inc_return_relaxed()
before taking the command-queue spinlock, then the following scenario
can occur:
CPU0 CPU1
msidata=0
msidata=1
insert cmd1
insert cmd0
smmu execute cmd1
smmu execute cmd0
poll timeout, because msidata=1 is overridden by
cmd0, that means VAL=0, sync_idx=1.
This is not a functional problem, since the caller will eventually either
timeout or exit due to another CMD_SYNC, however it's clearly not what
the code is supposed to be doing. Fix it, by incrementing the sequence
count with the command-queue lock held, allowing us to drop the atomic
operations altogether.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
[will: dropped the specialised cmd building routine for now]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'drivers/iommu')
| -rw-r--r-- | drivers/iommu/arm-smmu-v3.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index feef1226f705..48baffd07aef 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -567,7 +567,7 @@ struct arm_smmu_device { int gerr_irq; int combined_irq; - atomic_t sync_nr; + u32 sync_nr; unsigned long ias; /* IPA */ unsigned long oas; /* PA */ @@ -948,14 +948,13 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) struct arm_smmu_cmdq_ent ent = { .opcode = CMDQ_OP_CMD_SYNC, .sync = { - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), .msiaddr = virt_to_phys(&smmu->sync_count), }, }; - arm_smmu_cmdq_build_cmd(cmd, &ent); - spin_lock_irqsave(&smmu->cmdq.lock, flags); + ent.sync.msidata = ++smmu->sync_nr; + arm_smmu_cmdq_build_cmd(cmd, &ent); arm_smmu_cmdq_insert_cmd(smmu, cmd); spin_unlock_irqrestore(&smmu->cmdq.lock, flags); @@ -2180,7 +2179,6 @@ static int arm_smmu_init_structures(struct arm_smmu_device *smmu) { int ret; - atomic_set(&smmu->sync_nr, 0); ret = arm_smmu_init_queues(smmu); if (ret) return ret; |