Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit

[zhangfei.gao@xxxxxxxxxxx]

On 2022/4/11 下午10:36, Dave Hansen wrote:
> On 4/11/22 07:20, zhangfei.gao@xxxxxxxxxxx wrote:
> > > Is there nothing before this call trace?  Usually there will be at least
> > > some warning text.
> > I added dump_stack() in ioasid_free.
> Hold on a sec, though...
>
> What's the *problem* here?  Did something break or are you just saying
> that something looks weird to _you_?

After this, nginx is not working at all, and hardware reports error.
Suppose the the master use the ioasid for init, but got freed.

hardware reports:
[  152.731869] hisi_sec2 0000:76:00.0: qm_acc_do_task_timeout [error 
status=0x20] found
[  152.739657] hisi_sec2 0000:76:00.0: qm_acc_wb_not_ready_timeout 
[error status=0x40] found
[  152.747877] hisi_sec2 0000:76:00.0: sec_fsm_hbeat_rint [error 
status=0x20] found
[  152.755340] hisi_sec2 0000:76:00.0: Controller resetting...
[  152.762044] hisi_sec2 0000:76:00.0: QM mailbox operation timeout!
[  152.768198] hisi_sec2 0000:76:00.0: Failed to dump sqc!
[  152.773490] hisi_sec2 0000:76:00.0: Failed to drain out data for 
stopping!
[  152.781426] hisi_sec2 0000:76:00.0: QM mailbox is busy to start!
[  152.787468] hisi_sec2 0000:76:00.0: Failed to dump sqc!
[  152.792753] hisi_sec2 0000:76:00.0: Failed to drain out data for 
stopping!
[  152.800685] hisi_sec2 0000:76:00.0: QM mailbox is busy to start!
[  152.806730] hisi_sec2 0000:76:00.0: Failed to dump sqc!
[  152.812017] hisi_sec2 0000:76:00.0: Failed to drain out data for 
stopping!
[  152.819946] hisi_sec2 0000:76:00.0: QM mailbox is busy to start!
[  152.825992] hisi_sec2 0000:76:00.0: Failed to dump sqc!

Thanks

> For instance, if we have:
>
> 	nginx: ioasid_alloc()==1
> 	       fork(); // spawn the daemon
> 	       exit();
> 	       ioasid_free(1);
>
> and then a moment later:
>
> 	lynx:  ioasid_alloc()==1
> 	       fork();
> 	       exit();
> 	       ioasid_free(1);
>
> There's no problem.  The original nginx process with ioasid==1 exited.
> The fact that *some* process called nginx is still running doesn't mean
> that it still has a reference to asid==1.
>
> Are you sure the nginx process that allocated the ASID is the same
> process you see in ps?