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

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Date:   Mon, 11 Apr 2022 07:52:57 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "zhangfei.gao@...mail.com" <zhangfei.gao@...mail.com>,
        Joerg Roedel <joro@...tes.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        jean-philippe <jean-philippe@...aro.org>
Cc:     Ravi V Shankar <ravi.v.shankar@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        x86 <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit


On 4/11/22 07:44, zhangfei.gao@...mail.com wrote:
> On 2022/4/11 下午10:36, Dave Hansen wrote:
>> On 4/11/22 07:20, zhangfei.gao@...mail.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.