Date:   Mon, 15 Jul 2019 18:43:17 +0800
From:   Guoheyi <guoheyi@...wei.com>
To:     Marc Zyngier <marc.zyngier@....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 2019/7/15 17:07, Marc Zyngier wrote:
> 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.

I'm testing the patchset in 
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/vlpi-map-rework, 
not only the patch posted in the mail directly. The first patch 
*"**irqchip/gic-v3-its: Make vlpi_map allocations atomic" works well in 
our internal tree, and my new testing is against the other 3 patches in 
your vlpi-map-rework branch, as I promised. I'm sorry if I didn't state 
this clearly.

Heyi
*
>
> 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.
>>
>

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