* [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare
@ 2022-04-20 20:44 Elliot Berman
2022-04-21 7:44 ` Juergen Gross
0 siblings, 1 reply; 4+ messages in thread
From: Elliot Berman @ 2022-04-20 20:44 UTC (permalink / raw)
To: Juergen Gross, Srivatsa S. Bhat (VMware),
Alexey Makhalov, Catalin Marinas, Will Deacon
Cc: Prakruthi Deepak Heragu, virtualization, x86, linux-arm-kernel,
linux-kernel, Murali Nalajala, Elliot Berman
From: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
During hotplug, the stolen time data structure is unmapped and memset.
There is a possibility of the timer IRQ being triggered before memset
and stolen time is getting updated as part of this timer IRQ handler. This
causes the below crash in timer handler -
[ 3457.473139][ C5] Unable to handle kernel paging request at virtual address ffffffc03df05148
...
[ 3458.154398][ C5] Call trace:
[ 3458.157648][ C5] para_steal_clock+0x30/0x50
[ 3458.162319][ C5] irqtime_account_process_tick+0x30/0x194
[ 3458.168148][ C5] account_process_tick+0x3c/0x280
[ 3458.173274][ C5] update_process_times+0x5c/0xf4
[ 3458.178311][ C5] tick_sched_timer+0x180/0x384
[ 3458.183164][ C5] __run_hrtimer+0x160/0x57c
[ 3458.187744][ C5] hrtimer_interrupt+0x258/0x684
[ 3458.192698][ C5] arch_timer_handler_virt+0x5c/0xa0
[ 3458.198002][ C5] handle_percpu_devid_irq+0xdc/0x414
[ 3458.203385][ C5] handle_domain_irq+0xa8/0x168
[ 3458.208241][ C5] gic_handle_irq.34493+0x54/0x244
[ 3458.213359][ C5] call_on_irq_stack+0x40/0x70
[ 3458.218125][ C5] do_interrupt_handler+0x60/0x9c
[ 3458.223156][ C5] el1_interrupt+0x34/0x64
[ 3458.227560][ C5] el1h_64_irq_handler+0x1c/0x2c
[ 3458.232503][ C5] el1h_64_irq+0x7c/0x80
[ 3458.236736][ C5] free_vmap_area_noflush+0x108/0x39c
[ 3458.242126][ C5] remove_vm_area+0xbc/0x118
[ 3458.246714][ C5] vm_remove_mappings+0x48/0x2a4
[ 3458.251656][ C5] __vunmap+0x154/0x278
[ 3458.255796][ C5] stolen_time_cpu_down_prepare+0xc0/0xd8
[ 3458.261542][ C5] cpuhp_invoke_callback+0x248/0xc34
[ 3458.266842][ C5] cpuhp_thread_fun+0x1c4/0x248
[ 3458.271696][ C5] smpboot_thread_fn+0x1b0/0x400
[ 3458.276638][ C5] kthread+0x17c/0x1e0
[ 3458.280691][ C5] ret_from_fork+0x10/0x20
As a fix, disable the IRQs during hotplug until we unmap and memset the
stolen time structure.
Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
arch/arm64/kernel/paravirt.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
index 75fed4460407..fc05a08557e0 100644
--- a/arch/arm64/kernel/paravirt.c
+++ b/arch/arm64/kernel/paravirt.c
@@ -70,13 +70,16 @@ static u64 para_steal_clock(int cpu)
static int stolen_time_cpu_down_prepare(unsigned int cpu)
{
struct pv_time_stolen_time_region *reg;
+ unsigned long flags;
reg = this_cpu_ptr(&stolen_time_region);
if (!reg->kaddr)
return 0;
+ local_irq_save(flags);
memunmap(reg->kaddr);
memset(reg, 0, sizeof(*reg));
+ local_irq_restore(flags);
return 0;
}
--
2.25.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare
2022-04-20 20:44 [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare Elliot Berman
@ 2022-04-21 7:44 ` Juergen Gross
2022-04-21 9:10 ` Will Deacon
0 siblings, 1 reply; 4+ messages in thread
From: Juergen Gross @ 2022-04-21 7:44 UTC (permalink / raw)
To: Elliot Berman, Srivatsa S. Bhat (VMware),
Alexey Makhalov, Catalin Marinas, Will Deacon
Cc: Prakruthi Deepak Heragu, virtualization, x86, linux-arm-kernel,
linux-kernel, Murali Nalajala
[-- Attachment #1.1.1: Type: text/plain, Size: 2566 bytes --]
On 20.04.22 22:44, Elliot Berman wrote:
> From: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
>
> During hotplug, the stolen time data structure is unmapped and memset.
> There is a possibility of the timer IRQ being triggered before memset
> and stolen time is getting updated as part of this timer IRQ handler. This
> causes the below crash in timer handler -
>
> [ 3457.473139][ C5] Unable to handle kernel paging request at virtual address ffffffc03df05148
> ...
> [ 3458.154398][ C5] Call trace:
> [ 3458.157648][ C5] para_steal_clock+0x30/0x50
> [ 3458.162319][ C5] irqtime_account_process_tick+0x30/0x194
> [ 3458.168148][ C5] account_process_tick+0x3c/0x280
> [ 3458.173274][ C5] update_process_times+0x5c/0xf4
> [ 3458.178311][ C5] tick_sched_timer+0x180/0x384
> [ 3458.183164][ C5] __run_hrtimer+0x160/0x57c
> [ 3458.187744][ C5] hrtimer_interrupt+0x258/0x684
> [ 3458.192698][ C5] arch_timer_handler_virt+0x5c/0xa0
> [ 3458.198002][ C5] handle_percpu_devid_irq+0xdc/0x414
> [ 3458.203385][ C5] handle_domain_irq+0xa8/0x168
> [ 3458.208241][ C5] gic_handle_irq.34493+0x54/0x244
> [ 3458.213359][ C5] call_on_irq_stack+0x40/0x70
> [ 3458.218125][ C5] do_interrupt_handler+0x60/0x9c
> [ 3458.223156][ C5] el1_interrupt+0x34/0x64
> [ 3458.227560][ C5] el1h_64_irq_handler+0x1c/0x2c
> [ 3458.232503][ C5] el1h_64_irq+0x7c/0x80
> [ 3458.236736][ C5] free_vmap_area_noflush+0x108/0x39c
> [ 3458.242126][ C5] remove_vm_area+0xbc/0x118
> [ 3458.246714][ C5] vm_remove_mappings+0x48/0x2a4
> [ 3458.251656][ C5] __vunmap+0x154/0x278
> [ 3458.255796][ C5] stolen_time_cpu_down_prepare+0xc0/0xd8
> [ 3458.261542][ C5] cpuhp_invoke_callback+0x248/0xc34
> [ 3458.266842][ C5] cpuhp_thread_fun+0x1c4/0x248
> [ 3458.271696][ C5] smpboot_thread_fn+0x1b0/0x400
> [ 3458.276638][ C5] kthread+0x17c/0x1e0
> [ 3458.280691][ C5] ret_from_fork+0x10/0x20
>
> As a fix, disable the IRQs during hotplug until we unmap and memset the
> stolen time structure.
This will work for the call chain of your observed crash, but are
you sure that para_steal_clock() can't be called from another cpu
concurrently?
In case you verified this can't happen, you can add my:
Reviewed-by: Juergen Gross <jgross@suse.com>
Otherwise you either need to use RCU for doing the memunmap(), or a
lock to protect stolen_time_region.
Juergen
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[-- Attachment #2: OpenPGP digital signature --]
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare
2022-04-21 7:44 ` Juergen Gross
@ 2022-04-21 9:10 ` Will Deacon
2022-04-22 19:03 ` Elliot Berman
0 siblings, 1 reply; 4+ messages in thread
From: Will Deacon @ 2022-04-21 9:10 UTC (permalink / raw)
To: Juergen Gross
Cc: Elliot Berman, Srivatsa S. Bhat (VMware),
Alexey Makhalov, Catalin Marinas, Prakruthi Deepak Heragu,
virtualization, x86, linux-arm-kernel, linux-kernel,
Murali Nalajala
On Thu, Apr 21, 2022 at 09:44:28AM +0200, Juergen Gross wrote:
> On 20.04.22 22:44, Elliot Berman wrote:
> > From: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
> >
> > During hotplug, the stolen time data structure is unmapped and memset.
> > There is a possibility of the timer IRQ being triggered before memset
> > and stolen time is getting updated as part of this timer IRQ handler. This
> > causes the below crash in timer handler -
> >
> > [ 3457.473139][ C5] Unable to handle kernel paging request at virtual address ffffffc03df05148
> > ...
> > [ 3458.154398][ C5] Call trace:
> > [ 3458.157648][ C5] para_steal_clock+0x30/0x50
> > [ 3458.162319][ C5] irqtime_account_process_tick+0x30/0x194
> > [ 3458.168148][ C5] account_process_tick+0x3c/0x280
> > [ 3458.173274][ C5] update_process_times+0x5c/0xf4
> > [ 3458.178311][ C5] tick_sched_timer+0x180/0x384
> > [ 3458.183164][ C5] __run_hrtimer+0x160/0x57c
> > [ 3458.187744][ C5] hrtimer_interrupt+0x258/0x684
> > [ 3458.192698][ C5] arch_timer_handler_virt+0x5c/0xa0
> > [ 3458.198002][ C5] handle_percpu_devid_irq+0xdc/0x414
> > [ 3458.203385][ C5] handle_domain_irq+0xa8/0x168
> > [ 3458.208241][ C5] gic_handle_irq.34493+0x54/0x244
> > [ 3458.213359][ C5] call_on_irq_stack+0x40/0x70
> > [ 3458.218125][ C5] do_interrupt_handler+0x60/0x9c
> > [ 3458.223156][ C5] el1_interrupt+0x34/0x64
> > [ 3458.227560][ C5] el1h_64_irq_handler+0x1c/0x2c
> > [ 3458.232503][ C5] el1h_64_irq+0x7c/0x80
> > [ 3458.236736][ C5] free_vmap_area_noflush+0x108/0x39c
> > [ 3458.242126][ C5] remove_vm_area+0xbc/0x118
> > [ 3458.246714][ C5] vm_remove_mappings+0x48/0x2a4
> > [ 3458.251656][ C5] __vunmap+0x154/0x278
> > [ 3458.255796][ C5] stolen_time_cpu_down_prepare+0xc0/0xd8
> > [ 3458.261542][ C5] cpuhp_invoke_callback+0x248/0xc34
> > [ 3458.266842][ C5] cpuhp_thread_fun+0x1c4/0x248
> > [ 3458.271696][ C5] smpboot_thread_fn+0x1b0/0x400
> > [ 3458.276638][ C5] kthread+0x17c/0x1e0
> > [ 3458.280691][ C5] ret_from_fork+0x10/0x20
> >
> > As a fix, disable the IRQs during hotplug until we unmap and memset the
> > stolen time structure.
>
> This will work for the call chain of your observed crash, but are
> you sure that para_steal_clock() can't be called from another cpu
> concurrently?
Agreed, this needs checking as update_rq_clock() is called from all over the
place.
> In case you verified this can't happen, you can add my:
>
> Reviewed-by: Juergen Gross <jgross@suse.com>
>
> Otherwise you either need to use RCU for doing the memunmap(), or a
> lock to protect stolen_time_region.
Yes, I think RCU would make a lot of sense here, deferring the memunmap
until there are no longer any readers. The reader is currently doing:
if (!reg->kaddr)
return 0;
return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
so we'd also want an rcu_dereference() on reg->kaddr to avoid reading it
twice.
Will
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare
2022-04-21 9:10 ` Will Deacon
@ 2022-04-22 19:03 ` Elliot Berman
0 siblings, 0 replies; 4+ messages in thread
From: Elliot Berman @ 2022-04-22 19:03 UTC (permalink / raw)
To: Will Deacon, Juergen Gross
Cc: Srivatsa S. Bhat (VMware),
Alexey Makhalov, Catalin Marinas, Prakruthi Deepak Heragu,
virtualization, x86, linux-arm-kernel, linux-kernel,
Murali Nalajala
On 4/21/2022 2:10 AM, Will Deacon wrote:
> On Thu, Apr 21, 2022 at 09:44:28AM +0200, Juergen Gross wrote:
>> On 20.04.22 22:44, Elliot Berman wrote:
>>> From: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
>>>
>>> During hotplug, the stolen time data structure is unmapped and memset.
>>> There is a possibility of the timer IRQ being triggered before memset
>>> and stolen time is getting updated as part of this timer IRQ handler. This
>>> causes the below crash in timer handler -
>>>
>>> [ 3457.473139][ C5] Unable to handle kernel paging request at virtual address ffffffc03df05148
>>> ...
>>> [ 3458.154398][ C5] Call trace:
>>> [ 3458.157648][ C5] para_steal_clock+0x30/0x50
>>> [ 3458.162319][ C5] irqtime_account_process_tick+0x30/0x194
>>> [ 3458.168148][ C5] account_process_tick+0x3c/0x280
>>> [ 3458.173274][ C5] update_process_times+0x5c/0xf4
>>> [ 3458.178311][ C5] tick_sched_timer+0x180/0x384
>>> [ 3458.183164][ C5] __run_hrtimer+0x160/0x57c
>>> [ 3458.187744][ C5] hrtimer_interrupt+0x258/0x684
>>> [ 3458.192698][ C5] arch_timer_handler_virt+0x5c/0xa0
>>> [ 3458.198002][ C5] handle_percpu_devid_irq+0xdc/0x414
>>> [ 3458.203385][ C5] handle_domain_irq+0xa8/0x168
>>> [ 3458.208241][ C5] gic_handle_irq.34493+0x54/0x244
>>> [ 3458.213359][ C5] call_on_irq_stack+0x40/0x70
>>> [ 3458.218125][ C5] do_interrupt_handler+0x60/0x9c
>>> [ 3458.223156][ C5] el1_interrupt+0x34/0x64
>>> [ 3458.227560][ C5] el1h_64_irq_handler+0x1c/0x2c
>>> [ 3458.232503][ C5] el1h_64_irq+0x7c/0x80
>>> [ 3458.236736][ C5] free_vmap_area_noflush+0x108/0x39c
>>> [ 3458.242126][ C5] remove_vm_area+0xbc/0x118
>>> [ 3458.246714][ C5] vm_remove_mappings+0x48/0x2a4
>>> [ 3458.251656][ C5] __vunmap+0x154/0x278
>>> [ 3458.255796][ C5] stolen_time_cpu_down_prepare+0xc0/0xd8
>>> [ 3458.261542][ C5] cpuhp_invoke_callback+0x248/0xc34
>>> [ 3458.266842][ C5] cpuhp_thread_fun+0x1c4/0x248
>>> [ 3458.271696][ C5] smpboot_thread_fn+0x1b0/0x400
>>> [ 3458.276638][ C5] kthread+0x17c/0x1e0
>>> [ 3458.280691][ C5] ret_from_fork+0x10/0x20
>>>
>>> As a fix, disable the IRQs during hotplug until we unmap and memset the
>>> stolen time structure.
>>
>> This will work for the call chain of your observed crash, but are
>> you sure that para_steal_clock() can't be called from another cpu
>> concurrently?
>
> Agreed, this needs checking as update_rq_clock() is called from all over the
> place.
>
>> In case you verified this can't happen, you can add my:
>>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
>>
>> Otherwise you either need to use RCU for doing the memunmap(), or a
>> lock to protect stolen_time_region.
>
> Yes, I think RCU would make a lot of sense here, deferring the memunmap
> until there are no longer any readers. The reader is currently doing:
>
> if (!reg->kaddr)
> return 0;
>
> return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
>
> so we'd also want an rcu_dereference() on reg->kaddr to avoid reading it
> twice.
>
> Will
We have seen this particular stack many times in our testing, but not
any other way. Will's comments are agreeable, I'll send out an updated
patch.
Thanks,
Elliot
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-04-22 22:31 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-04-20 20:44 [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare Elliot Berman
2022-04-21 7:44 ` Juergen Gross
2022-04-21 9:10 ` Will Deacon
2022-04-22 19:03 ` Elliot Berman
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