Messages in this thread Patch in this message | | | From | Zhen Lei <> | Subject | [PATCH v3 1/2] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout | Date | Wed, 15 Aug 2018 18:23:01 +0800 |
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The condition "(int)(VAL - sync_idx) >= 0" to break loop in function __arm_smmu_sync_poll_msi requires that sync_idx must be increased monotonously according to the sequence of the CMDs in the cmdq.
But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected by spinlock, so the following scenarios may appear: 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, just make the caller wait for a long time until TIMEOUT. It's rare to happen, because any other CMD_SYNCs during the waiting period will break it.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- drivers/iommu/arm-smmu-v3.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 1d64710..3f5c236 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -566,7 +566,7 @@ 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 */ @@ -775,6 +775,11 @@ static int queue_remove_raw(struct arm_smmu_queue *q, u64 *ent) return 0; }
+static inline void arm_smmu_cmdq_sync_set_msidata(u64 *cmd, u32 msidata) +{ + cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, msidata); +} + /* High-level queue accessors */ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) { @@ -836,7 +841,6 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV); cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH); cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB); - cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIDATA, ent->sync.msidata); cmd[1] |= ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; break; default: @@ -947,7 +951,6 @@ 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), }, }; @@ -955,6 +958,8 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) arm_smmu_cmdq_build_cmd(cmd, &ent);
spin_lock_irqsave(&smmu->cmdq.lock, flags); + ent.sync.msidata = ++smmu->sync_nr; + arm_smmu_cmdq_sync_set_msidata(cmd, ent.sync.msidata); arm_smmu_cmdq_insert_cmd(smmu, cmd); spin_unlock_irqrestore(&smmu->cmdq.lock, flags);
@@ -2179,7 +2184,6 @@ 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; -- 1.8.3
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