From: Zhen Lei thunder.leizhen@huawei.com
[ Upstream commit 0f02477d16980938a84aba8688a4e3a303306116 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/arm-smmu-v3.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 40fbf20d69e5a..2ab7100bcff12 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 */ @@ -964,14 +964,13 @@ 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);
@@ -2196,7 +2195,6 @@ 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;