linux-kernel - Re: [PATCH] firmware: arm_sdei: pass sdei_api_event

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Message-ID: <6b36e47e-3fd6-f7fe-7b88-ed56cd3c9b4e@linux.alibaba.com>
Date:   Tue, 19 Oct 2021 11:35:43 +0800
From:   乱石 <zhangliguang@...ux.alibaba.com>
To:     James Morse <james.morse@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firmware: arm_sdei: pass sdei_api_event_register right
 parameters

Hi James,

在 2021/10/19 1:32, James Morse 写道:
> Hi Liguang,
>
> On 11/10/2021 06:40, 乱石 wrote:
>> 在 2021/10/9 1:39, James Morse 写道:
>>> On 10/09/2021 05:01, Liguang Zhang wrote:
>>>> Function _local_event_enable is used for private sdei event
>>>> registeration called by sdei_event_register. We should pass
>>> (registration)
>>>> sdei_api_event_register right flag and mpidr parameters, otherwise atf
>>>> may trigger assert errors.
>>>> diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
>>>> index a7e762c352f9..0736752dadde 100644
>>>> --- a/drivers/firmware/arm_sdei.c
>>>> +++ b/drivers/firmware/arm_sdei.c
>>>> @@ -558,14 +558,16 @@ static int sdei_api_event_register(u32 event_num, unsigned long
>>>> entry_point,
>>>>    static void _local_event_register(void *data)
>>>>    {
>>>>        int err;
>>>> +    u64 mpidr;
>>>>        struct sdei_registered_event *reg;
>>>>        struct sdei_crosscall_args *arg = data;
>>>>          WARN_ON(preemptible());
>>>>    +    mpidr = read_cpuid_mpidr();
>>>>        reg = per_cpu_ptr(arg->event->private_registered, smp_processor_id());
>>>>        err = sdei_api_event_register(arg->event->event_num, sdei_entry_point,
>>>> -                      reg, 0, 0);
>>>> +                      reg, SDEI_EVENT_REGISTER_RM_PE, mpidr);
>>> Hmmm, this looks like a bug in TFA.
>>>
>>> 5.1.2.2 "Parameters" of DEN 0054B has:
>>> | Routing mode is valid only for a shared event. For a private event, the routing mode is
>>> | ignored.
>>>
>>> Worse, the mpidr field has:
>>> | Currently the format is defined only when the selected routing mode is RM_PE.
>
>> For a private event, we route SDEI_EVENT_REGISTER_RM_PE and mpidr parameters may be more
>> rationable.
> You are making this call from Linux?
>
> This isn't valid for private events. Private events are private to the CPU - they can only
> be reset, register and taken on that CPU. The specification for SDEI_EVENT_ROUTING_SET has
> this:
> | This call is used to change the routing information of a shared event.
>
> To borrow the GIC's terms: Private events are like PPI, Shared events are like SPI.
>
>
>>> Over in trusted firmware land:
>>>
>>> https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/tree/services/std_svc/sdei/sdei_main.c?h=v2.5#n361
>>>
>>>
>>> | static int64_t sdei_event_register(int ev_num,
>>> |                 uint64_t ep,
>>> |                 uint64_t arg,
>>> |                 uint64_t flags,
>>> |                uint64_t mpidr)
>>> | {
>>>
>>> |    /* Private events always target the PE */
>>> |    if (is_event_private(map))
>>> |        flags = SDEI_REGF_RM_PE;
>>>
>>> It looks like this re-uses the 'caller specified the routing' code, but didn't update the
>>> mpidr.
>>>
>>>
>>> You mention TFA takes an assert failure, I assume that brings the machine down.
>>> (Presumably you don't have a CPU with an affinity of zero.)
>> Yes, that brings the machine down. In opensource ATF, CPU with an affinity of zero.
>>
>> The problem backaround:
>>
>> we use local secure arch timer as sdei watchdog timer
> Is that an SPI? If so, you should really be generating a shared event.

It's an PPI, secured arch timer used for hardlockup detection.


>
>
>> for hardlockup detection, in  os
>> panic ,we mask sdei event, then trigger the assert
>> if (se->reg_flags == SDEI_REGF_RM_PE)
>>
>>      assert(se->affinity == my_mpidr);
>
> I'm not sure where this code in TFA is, but RM_PE for a private event is going to hit this
> on all but one CPU. You shouldn't be able to set RM_PE for a private event.
>
>
> I assume this is the TFA side of the problem from your colleague:
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/11393
>
>
> Does the problem occur with this TFA patch applied, and without any attempt to mess with
> the routing of per-cpu/private events?

Thanks for your reply. With the patch applied, the problem resolved.


Thanks,

Liguang

>
>
> Thanks,
>
> James