Re: ARM/gic-v4: deadlock occurred

[Heyi Guo <guoheyi@huawei.com>]

BTW since its_irq_set_vcpu_affinity() is already in atomic context, do we really need a separate lock its_dev->event_map.vlpi_lock? I didn't find anywhere outside its_irq_set_vcpu_affinity() call chain acquires this lock.

Thanks,

Heyi


On 2019/5/5 18:38, Marc Zyngier wrote:
> [+ kvmarm]
>
> Hi Heyi,
>
> On Sun, 05 May 2019 03:26:18 +0100,
> Heyi Guo <guoheyi@huawei.com> wrote:
>> Hi folks,
>>
>> We observed deadlocks after enabling GICv4 and PCI passthrough on
>> ARM64 virtual machines, when not pinning VCPU to physical CPU.
>>
>> We observed below warnings after enabling lockdep debug in kernel:
>>
>> [  362.847021] =====================================================
>> [  362.855643] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
>> [  362.864840] 4.19.34+ #7 Tainted: G        W
>> [  362.872314] -----------------------------------------------------
>> [  362.881034] CPU 0/KVM/51468 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
>> [  362.890504] 00000000659c1dc9 (fs_reclaim){+.+.}, at: fs_reclaim_acquire.part.22+0x0/0x48
>> [  362.901413]
>> [  362.901413] and this task is already holding:
>> [  362.912976] 000000007318873f (&dev->event_map.vlpi_lock){....}, at: its_irq_set_vcpu_affinity+0x134/0x638
>> [  362.928626] which would create a new lock dependency:
>> [  362.936837]  (&dev->event_map.vlpi_lock){....} -> (fs_reclaim){+.+.}
>> [  362.946449]
>> [  362.946449] but this new dependency connects a HARDIRQ-irq-safe lock:
>> [  362.960877]  (&irq_desc_lock_class){-.-.}
>> [  362.960880]
>> [  362.960880] ... which became HARDIRQ-irq-safe at:
>> [  362.981234]   lock_acquire+0xf0/0x258
>> [  362.988337]   _raw_spin_lock+0x54/0x90
>> [  362.995543]   handle_fasteoi_irq+0x2c/0x198
>> [  363.003205]   generic_handle_irq+0x34/0x50
>> [  363.010787]   __handle_domain_irq+0x68/0xc0
>> [  363.018500]   gic_handle_irq+0xf4/0x1e0
>> [  363.025913]   el1_irq+0xc8/0x180
>> [  363.032683]   _raw_spin_unlock_irq+0x40/0x60
>> [  363.040512]   finish_task_switch+0x98/0x258
>> [  363.048254]   __schedule+0x350/0xca8
>> [  363.055359]   schedule+0x40/0xa8
>> [  363.062098]   worker_thread+0xd8/0x410
>> [  363.069340]   kthread+0x134/0x138
>> [  363.076070]   ret_from_fork+0x10/0x18
>> [  363.083111]
>> [  363.083111] to a HARDIRQ-irq-unsafe lock:
>> [  363.095213]  (fs_reclaim){+.+.}
>> [  363.095216]
>> [  363.095216] ... which became HARDIRQ-irq-unsafe at:
>> [  363.114527] ...
>> [  363.114530]   lock_acquire+0xf0/0x258
>> [  363.126269]   fs_reclaim_acquire.part.22+0x3c/0x48
>> [  363.134206]   fs_reclaim_acquire+0x2c/0x38
>> [  363.141363]   kmem_cache_alloc_trace+0x44/0x368
>> [  363.148892]   acpi_os_map_iomem+0x9c/0x208
>> [  363.155934]   acpi_os_map_memory+0x28/0x38
>> [  363.162831]   acpi_tb_acquire_table+0x58/0x8c
>> [  363.170021]   acpi_tb_validate_table+0x34/0x58
>> [  363.177162]   acpi_tb_get_table+0x4c/0x90
>> [  363.183741]   acpi_get_table+0x94/0xc4
>> [  363.190020]   find_acpi_cpu_topology_tag+0x54/0x240
>> [  363.197404]   find_acpi_cpu_topology_package+0x28/0x38
>> [  363.204985]   init_cpu_topology+0xdc/0x1e4
>> [  363.211498]   smp_prepare_cpus+0x2c/0x108
>> [  363.217882]   kernel_init_freeable+0x130/0x508
>> [  363.224699]   kernel_init+0x18/0x118
>> [  363.230624]   ret_from_fork+0x10/0x18
>> [  363.236611]
>> [  363.236611] other info that might help us debug this:
>> [  363.236611]
>> [  363.251604] Chain exists of:
>> [  363.251604]   &irq_desc_lock_class --> &dev->event_map.vlpi_lock --> fs_reclaim
>> [  363.251604]
>> [  363.270508]  Possible interrupt unsafe locking scenario:
>> [  363.270508]
>> [  363.282238]        CPU0                    CPU1
>> [  363.289228]        ----                    ----
>> [  363.296189]   lock(fs_reclaim);
>> [  363.301726]                                local_irq_disable();
>> [  363.310122] lock(&irq_desc_lock_class);
>> [  363.319143] lock(&dev->event_map.vlpi_lock);
>> [  363.328617]   <Interrupt>
>> [  363.333713]     lock(&irq_desc_lock_class);
>> [  363.340414]
>> [  363.340414]  *** DEADLOCK ***
>> [  363.340414]
>> [  363.353682] 5 locks held by CPU 0/KVM/51468:
>> [  363.360412]  #0: 00000000eeb852a5 (&vdev->igate){+.+.}, at: vfio_pci_ioctl+0x2f8/0xed0
>> [  363.370915]  #1: 000000002ab491f7 (lock#9){+.+.}, at: irq_bypass_register_producer+0x6c/0x1d0
>> [  363.382139]  #2: 000000000d9fd5c6 (&its->its_lock){+.+.}, at: kvm_vgic_v4_set_forwarding+0xd0/0x188
>> [  363.396625]  #3: 00000000232bdc47 (&irq_desc_lock_class){-.-.}, at: __irq_get_desc_lock+0x60/0xa0
>> [  363.408486]  #4: 000000007318873f (&dev->event_map.vlpi_lock){....}, at: its_irq_set_vcpu_affinity+0x134/0x638
>>
>>
>> Then we found that irq_set_vcpu_affinity() in kernel/irq/manage.c
>> aquires an antomic context by irq_get_desc_lock() at the beginning,
>> but in its_irq_set_vcpu_affinity()
>> (drivers/irqchip/irq-gic-v3-its.c) we are still using mutext_lock,
>> kcalloc, kfree, etc, which we think should be forbidden in atomic
>> context.
>>
>> Though the issue is observed in 4.19.34, we don't find any related
>> fixes in the mainline yet.
> Thanks for the report. Given that you're the only users of GICv4,
> you're bound to find a number of these issues.
>
> Can you try the patch below and let me know whether it helps? This is
> the simplest thing I can think off to paper over the issue, but is
> isn't pretty, and I'm looking at possible alternatives (ideally, we'd
> be able to allocate the map outside of the irqdesc lock, but this
> requires some API change between KVM, the GICv4 layer and the ITS
> code).
>
> Note that I'm travelling for the next two weeks without access to my
> test rig, so I'm relying on you to test this stuff.
>
> Thanks,
>
> 	M.
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 7577755bdcf4..18aa04b6a9f4 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -142,7 +142,7 @@ struct event_lpi_map {
>   	u16			*col_map;
>   	irq_hw_number_t		lpi_base;
>   	int			nr_lpis;
> -	struct mutex		vlpi_lock;
> +	raw_spinlock_t		vlpi_lock;
>   	struct its_vm		*vm;
>   	struct its_vlpi_map	*vlpi_maps;
>   	int			nr_vlpis;
> @@ -1263,13 +1263,13 @@ static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
>   	if (!info->map)
>   		return -EINVAL;
>   
> -	mutex_lock(&its_dev->event_map.vlpi_lock);
> +	raw_spin_lock(&its_dev->event_map.vlpi_lock);
>   
>   	if (!its_dev->event_map.vm) {
>   		struct its_vlpi_map *maps;
>   
>   		maps = kcalloc(its_dev->event_map.nr_lpis, sizeof(*maps),
> -			       GFP_KERNEL);
> +			       GFP_ATOMIC);
>   		if (!maps) {
>   			ret = -ENOMEM;
>   			goto out;
> @@ -1312,7 +1312,7 @@ static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
>   	}
>   
>   out:
> -	mutex_unlock(&its_dev->event_map.vlpi_lock);
> +	raw_spin_unlock(&its_dev->event_map.vlpi_lock);
>   	return ret;
>   }
>   
> @@ -1322,7 +1322,7 @@ static int its_vlpi_get(struct irq_data *d, struct its_cmd_info *info)
>   	u32 event = its_get_event_id(d);
>   	int ret = 0;
>   
> -	mutex_lock(&its_dev->event_map.vlpi_lock);
> +	raw_spin_lock(&its_dev->event_map.vlpi_lock);
>   
>   	if (!its_dev->event_map.vm ||
>   	    !its_dev->event_map.vlpi_maps[event].vm) {
> @@ -1334,7 +1334,7 @@ static int its_vlpi_get(struct irq_data *d, struct its_cmd_info *info)
>   	*info->map = its_dev->event_map.vlpi_maps[event];
>   
>   out:
> -	mutex_unlock(&its_dev->event_map.vlpi_lock);
> +	raw_spin_unlock(&its_dev->event_map.vlpi_lock);
>   	return ret;
>   }
>   
> @@ -1344,7 +1344,7 @@ static int its_vlpi_unmap(struct irq_data *d)
>   	u32 event = its_get_event_id(d);
>   	int ret = 0;
>   
> -	mutex_lock(&its_dev->event_map.vlpi_lock);
> +	raw_spin_lock(&its_dev->event_map.vlpi_lock);
>   
>   	if (!its_dev->event_map.vm || !irqd_is_forwarded_to_vcpu(d)) {
>   		ret = -EINVAL;
> @@ -1374,7 +1374,7 @@ static int its_vlpi_unmap(struct irq_data *d)
>   	}
>   
>   out:
> -	mutex_unlock(&its_dev->event_map.vlpi_lock);
> +	raw_spin_unlock(&its_dev->event_map.vlpi_lock);
>   	return ret;
>   }
>   
> @@ -2436,7 +2436,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
>   	dev->event_map.col_map = col_map;
>   	dev->event_map.lpi_base = lpi_base;
>   	dev->event_map.nr_lpis = nr_lpis;
> -	mutex_init(&dev->event_map.vlpi_lock);
> +	raw_spin_lock_init(&dev->event_map.vlpi_lock);
>   	dev->device_id = dev_id;
>   	INIT_LIST_HEAD(&dev->entry);
>   
>


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