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

zhangfei.gao
2022-04-12T15:35:47Z

Hi, Fenghua

On 2022/4/12 下午9:41, Fenghua Yu wrote:
> Hi, Zhangfei,
>
> On Tue, Apr 12, 2022 at 03:04:09PM +0800, zhangfei.gao@foxmail.com wrote:
>>
>> On 2022/4/11 下午10:52, Dave Hansen wrote:
>>> On 4/11/22 07:44, zhangfei.gao@foxmail.com wrote:
>>>> On 2022/4/11 下午10:36, Dave Hansen wrote:
>>>>> On 4/11/22 07:20, zhangfei.gao@foxmail.com 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!
>>> That would have been awfully handy information to have in an initial bug report. :)
>>> Is there a chance you could dump out that ioasid alloc *and* free information in ioasid_alloc/free()? This could be some kind of problem with the allocator, or with copying the ioasid at fork.
>> The issue is nginx master process init resource, start daemon process, then
>> master process quit and free ioasid.
>> The daemon nginx process is not the original master process.
>>
>> master process:  init resource
>> driver -> iommu_sva_bind_device -> ioasid_alloc
> Which code in the master process/daemon calls driver->iommu_sva_unbind_device?
Our calling sequence is nginx -> openssl -> openssl engine ->  kernel driver
The calling entrence should be ngx_ssl_init : OPENSSL_config(NULL);

nginx:
src/event/ngx_event_openssl.c
ngx_ssl_init
if (OPENSSL_init_ssl(OPENSSL_INIT_LOAD_CONFIG, NULL) == 0)

I add some print.

/usr/local/nginx$ sudo sbin/nginx
ngx_ssl_init pid=2361
bind_fn
ngx_openssl_create_conf pid=2361
hisi sec init Kunpeng920!
ngx_ssl_create pid=2361
ngx_ssl_certificates pid=2361
ngx_ssl_certificate pid=2361
uadk_e_wd_digest_init
hisi sec init Kunpeng920!
ngx_ssl_ciphers pid=2361
ngx_daemon pid=2361 fork daemon
master pid=2361 will exit                                // here master
process is exit
fork return 0 pid=2364                                       // here
daemon process started
ngx_daemon fork ngx_pid=2364, ngx_parent=2361
$ ps -aux | grep nginx
root        2364  0.0  0.0  31324 15380 ?        Ssl  15:21   0:00
nginx: master process sbin/nginx
nobody      2366  0.0  0.0  32304 16448 ?        Sl   15:21   0:00
nginx: worker process
linaro      2371  0.0  0.0   7696  2048 pts/0    S+   15:22   0:00 grep
--color=auto nginx

nginx
src/os/unix/ngx_daemon.c
ngx_daemon(ngx_log_t *log)
{
int  fd;

switch (fork()) {
case -1:
ngx_log_error(NGX_LOG_EMERG, log, ngx_errno, "fork() failed");
return NGX_ERROR;

case 0:
// here fork daemon process
break;

default:
// master process directly exit, and release mm as well as ioasid
exit(0);
}

// only daemon process
ngx_parent = ngx_pid;
ngx_pid = ngx_getpid();

>
>> nginx : ngx_daemon
>> fork daemon, without add mm's refcount.
>>
>> src/os/unix/ngx_daemon.c
>> ngx_daemon(ngx_log_t *log)
>> {
>>     int  fd;
>>
>>     switch (fork()) {
>>     case -1:
>>         ngx_log_error(NGX_LOG_EMERG, log, ngx_errno, "fork() failed");
>>         return NGX_ERROR;
>>
>>     case 0:        // here master process is quit directly and will be
>> released.
>>         break;
>>
>>     default:
>>         exit(0);
>>     }
>> // here daemon process take control.
>>     ngx_parent = ngx_pid;
>>     ngx_pid = ngx_getpid();
>>
>>
>> fork.c
>> copy_mm
>>         if (clone_flags & CLONE_VM) {
>>                 mmget(oldmm);
>>                 mm = oldmm;
>>         } else {
>>                 mm = dup_mm(tsk, current->mm);    // here daemon process
>> handling without mmget.
>>
>> master process quit, mmput ->  mm_pasid_drop->ioasid_free
>> But this ignore driver's iommu_sva_unbind_device function,
>> iommu_sva_bind_device and iommu_sva_unbind_device are not pair,  So driver
>> does not know ioasid is freed.
>>
>> Any suggestion?
> ioasid is per process or per mm. A daemon process shouldn't share the same
> ioasid with any other process with even its parent process. Its parent gets
> an ioasid and frees it on exit. The ioasid is gone and shouldn't be used
> by its child process.
>
> Each daemon process should call driver -> iommu_sva_bind_device -> ioasid_alloc
> to get its own ioasid/PASID. On daemon quit, the ioasid is freed.
>
> That means nqnix needs to be changed.

Agree with Dave, I think user space should not be broken.

Thanks