Date:   Mon, 15 Jul 2019 10:07:59 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Guoheyi <guoheyi@...wei.com>
Cc:     linux-kernel@...r.kernel.org,
        wanghaibin 00208455 <wanghaibin.wang@...wei.com>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>
Subject: Re: ARM/gic-v4: deadlock occurred

On 15/07/2019 07:32, Guoheyi wrote:
> Hi Marc,
> 
> The issue only occurs after applying the vlpi_map_rework patches, and we 
> can see the patches only affect VM; it changes its_create_device() a 
> little so it may affect host booting in some ways, so I took the lazy 
> way to send it out for some insights.
> 
> I am suspecting below code; if alloc_lpis == false, what will happen? 

If !alloc_lpis, then we don't allocate the lpi_map, which is the
intended effect.

> Anyway, I will investigate more on this.
> 
> 
> 	if  (alloc_lpis)  {
> 		lpi_map  =  its_lpi_alloc(nvecs,  &lpi_base,  &nr_lpis);
> 		if  (lpi_map)
> 			col_map  =  kcalloc(nr_lpis,  sizeof(*col_map),
> 					GFP_KERNEL);
> 	}  else  {
> 		col_map  =  kcalloc(nr_ites,  sizeof(*col_map),  GFP_KERNEL);
> 		nr_lpis  =  0;
> 		lpi_base  =  0;
> 	}
> 	if  (its->is_v4)
> 		vlpi_map  =  kcalloc(nr_lpis,  sizeof(*vlpi_map),  GFP_KERNEL);
> 
> 	if  (!dev  ||  !itt  ||   !col_map  ||  (!lpi_map  &&  alloc_lpis)  ||
> 	(!vlpi_map  &&  its->is_v4))  {
> 		kfree(dev);
> 		kfree(itt);
> 		kfree(lpi_map);
> 		kfree(col_map);
> 		kfree(vlpi_map);
> 		return  NULL;
> 	}

How does this relate to the patch posted in this discussion? The
proposed changes turn the locking from a mutex into a raw_spinlock.

That's not to say there is no bug in the GICv4 code, but I'd expect a
bit more analysis before you start pointing at random pieces of code
without establishing any link between effects and possible causes.

Thanks,

	M.
> 
> 
> Thanks,
> 
> Heyi
> 
> 
> On 2019/7/13 19:37, Marc Zyngier wrote:
>> On Sat, 13 Jul 2019 19:08:57 +0800
>> Guoheyi <guoheyi@...wei.com> wrote:
>>
>> Hi Heyi,
>>
>>> Hi Marc,
>>>
>>> Really sorry for the delay of testing the rework patches. I picked up
>>> the work these days and applied the patches to our 4.19.36 stable
>>> branch. However, I got below panic during the boot process of host
>>> (not yet to boot guests).
>>>
>>> I supposed the result was not related with my testing kernel version,
>>> for we don't have many differences in ITS driver; I can test against
>>> mainline if you think it is necessary.
>> In general, please report bugs against mainline. There isn't much I can
>> do about your private tree...
>>
>> That being said, a couple of comments below.
>>
>>> Thanks,
>>>
>>> Heyi
>>>
>>>
>>> [   16.990413] iommu: Adding device 0000:00:00.0 to group 6
>>> [   17.000691] pcieport 0000:00:00.0: Signaling PME with IRQ 133
>>> [   17.006456] pcieport 0000:00:00.0: AER enabled with IRQ 134
>>> [   17.012151] iommu: Adding device 0000:00:08.0 to group 7
>>> [   17.018575] Unable to handle kernel paging request at virtual address 00686361635f746f
>>> [   17.026467] Mem abort info:
>>> [   17.029251]   ESR = 0x96000004
>>> [   17.032313]   Exception class = DABT (current EL), IL = 32 bits
>>> [   17.038207]   SET = 0, FnV = 0
>>> [   17.041258]   EA = 0, S1PTW = 0
>>> [   17.044391] Data abort info:
>>> [   17.047260]   ISV = 0, ISS = 0x00000004
>>> [   17.051081]   CM = 0, WnR = 0
>>> [   17.054035] [00686361635f746f] address between user and kernel address ranges
>>> [   17.061140] Internal error: Oops: 96000004 [#1] SMP
>>> [   17.065997] Process kworker/0:4 (pid: 889, stack limit = 0x(____ptrval____))
>>> [   17.073013] CPU: 0 PID: 889 Comm: kworker/0:4 Not tainted 4.19.36+ #8
>>> [   17.079422] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 0.52 06/20/2019
>>> [   17.086788] Workqueue: events work_for_cpu_fn
>>> [   17.091126] pstate: 20c00009 (nzCv daif +PAN +UAO)
>>> [   17.095895] pc : __kmalloc_track_caller+0xb0/0x2a0
>>> [   17.100662] lr : __kmalloc_track_caller+0x64/0x2a0
>>> [   17.105429] sp : ffff00002920ba00
>>> [   17.108728] x29: ffff00002920ba00 x28: ffff802cb6792780
>>> [   17.114015] x27: 00000000006080c0 x26: 00000000006000c0
>>> [   17.119302] x25: ffff0000084c8a00 x24: ffff802cbfc0fc00
>>> [   17.124588] x23: ffff802cbfc0fc00 x22: ffff0000084c8a00
>>> [   17.129875] x21: 0000000000000004 x20: 00000000006000c0
>>> [   17.135161] x19: 65686361635f746f x18: ffffffffffffffff
>>> [   17.140448] x17: 000000000000000e x16: 0000000000000007
>>> [   17.145734] x15: ffff000009119708 x14: 0000000000000000
>>> [   17.151021] x13: 0000000000000003 x12: 0000000000000000
>>> [   17.156307] x11: 0000000005f5e0ff x10: ffff00002920bb80
>>> [   17.161594] x9 : 00000000ffffffd0 x8 : 0000000000000098
>>> [   17.166880] x7 : ffff00002920bb80 x6 : ffff000008a8cb98
>>> [   17.172167] x5 : 000000000000a705 x4 : ffff803f802d22e0
>>> [   17.177453] x3 : ffff00002920b990 x2 : ffff7e00b2dafd00
>>> [   17.182740] x1 : 0000803f77476000 x0 : 0000000000000000
>>> [   17.188027] Call trace:
>>> [   17.190461]  __kmalloc_track_caller+0xb0/0x2a0
>>> [   17.194886]  kvasprintf+0x7c/0x108
>>> [   17.198271]  kasprintf+0x60/0x80
>>> [   17.201488]  populate_msi_sysfs+0xe4/0x250
>>> [   17.205564]  __pci_enable_msi_range+0x278/0x450
>>> [   17.210073]  pci_alloc_irq_vectors_affinity+0xd4/0x110
>>> [   17.215188]  pcie_port_device_register+0x134/0x558
>>> [   17.219955]  pcie_portdrv_probe+0x3c/0xf0
>>> [   17.223947]  local_pci_probe+0x44/0xa8
>>> [   17.227679]  work_for_cpu_fn+0x20/0x30
>>> [   17.231411]  process_one_work+0x1b4/0x3f8
>>> [   17.235401]  worker_thread+0x210/0x470
>>> [   17.239134]  kthread+0x134/0x138
>>> [   17.242348]  ret_from_fork+0x10/0x18
>>> [   17.245907] Code: f100005f fa401a64 54000bc0 b9402300 (f8606a66)
>>> [   17.251970] kernel fault(0x1) notification starting on CPU 0
>>> [   17.257602] kernel fault(0x1) notification finished on CPU 0
>>> [   17.263234] Modules linked in:
>>> [   17.266277] ---[ end trace 023e6b19cb68b94f ]---
>> What in this trace makes you think that this has anything to do with an
>> ITS change? The system crashes in a completely unrelated piece of code.
>> Also, if you look at the VA that indicates the crash, it should be
>> obvious that this isn't a kernel address. Worse, this is a piece of
>> ASCII text:
>>
>> $ echo 00686361635f746f | xxd -r -p
>> hcac_to
>>
>> This tends to indicate some memory form of corruption ("hcac_to" looks
>> like the begining of a symbol), and I'm not sure how the ITS would be
>> involved in this... Furthermore, this happens on the host at boot time,
>> while the patch you suspect only affects VMs...
>>
>> I think you need to spend more time analysing this issue.
>>
>> Thanks,
>>
>> 	M.
> 
> 


-- 
Jazz is not dead. It just smells funny...

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