summaryrefslogtreecommitdiff
path: root/drivers/iommu
diff options
context:
space:
mode:
authorZhen Lei <thunder.leizhen@huawei.com>2018-08-19 10:51:10 +0300
committerWill Deacon <will.deacon@arm.com>2018-10-01 15:01:30 +0300
commit0f02477d16980938a84aba8688a4e3a303306116 (patch)
treeb56b2730a54ece3940ce9a735a62c9730d63c7bf /drivers/iommu
parent85c7a0f1ef624ef58173ef52ea77780257bdfe04 (diff)
downloadlinux-0f02477d16980938a84aba8688a4e3a303306116.tar.xz
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.c8
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;