linux-kernel - Re: [PATCH] irqchip/gic-v3-its: Don't confuse get_vlpi

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Message-ID: <b447c84c609e9799bbac6aada2ffb9ce@kernel.org>
Date:   Wed, 22 Jan 2020 15:22:58 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Zenghui Yu <yuzenghui@...wei.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jason@...edaemon.net,
        wanghaibin.wang@...wei.com
Subject: Re: [PATCH] irqchip/gic-v3-its: Don't confuse get_vlpi_map() by
 writing DB config

On 2020-01-22 11:29, Zenghui Yu wrote:
> Hi Marc,
> 
> On 2020/1/22 18:44, Marc Zyngier wrote:
>> Hi Zenghui,
>> 
>> Thanks for this.
>> 
>> On 2020-01-22 08:56, Zenghui Yu wrote:
>>> When we're writing config for the doorbell interrupt, get_vlpi_map() 
>>> will
>>> get confused by doorbell's d->parent_data hack and find the wrong 
>>> its_dev
>>> as chip data and the wrong event.
>>> 
>>> Fix this issue by making sure no doorbells will be involved before 
>>> invoking
>>> get_vlpi_map(), which restore some of the logic in 
>>> lpi_write_config().
>>> 
>>> Fixes: c1d4d5cd203c ("irqchip/gic-v3-its: Add its_vlpi_map helpers")
>>> Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
>>> ---
>>> 
>>> This is based on mainline and can't be directly applied to the 
>>> current
>>> irqchip-next.
>>> 
>>>  drivers/irqchip/irq-gic-v3-its.c | 5 +++--
>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>> 
>>> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
>>> b/drivers/irqchip/irq-gic-v3-its.c
>>> index e05673bcd52b..cc8a4fcbd6d6 100644
>>> --- a/drivers/irqchip/irq-gic-v3-its.c
>>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>>> @@ -1181,12 +1181,13 @@ static struct its_vlpi_map
>>> *get_vlpi_map(struct irq_data *d)
>>> 
>>>  static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
>>>  {
>>> -    struct its_vlpi_map *map = get_vlpi_map(d);
>>>      irq_hw_number_t hwirq;
>>>      void *va;
>>>      u8 *cfg;
>>> 
>>> -    if (map) {
>>> +    if (irqd_is_forwarded_to_vcpu(d)) {
>>> +        struct its_vlpi_map *map = get_vlpi_map(d);
>>> +
>>>          va = page_address(map->vm->vprop_page);
>>>          hwirq = map->vintid;
>> 
>> Shouldn't we fix get_vlpi_map() instead? Something like (untested):
>> 
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
>> b/drivers/irqchip/irq-gic-v3-its.c
>> index e05673bcd52b..b704214390c0 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -1170,13 +1170,14 @@ static void its_send_vclear(struct its_device 
>> *dev, u32 event_id)
>>    */
>>   static struct its_vlpi_map *get_vlpi_map(struct irq_data *d)
>>   {
>> -    struct its_device *its_dev = irq_data_get_irq_chip_data(d);
>> -    u32 event = its_get_event_id(d);
>> +    if (irqd_is_forwarded_to_vcpu(d)) {
>> +        struct its_device *its_dev = irq_data_get_irq_chip_data(d);
>> +        u32 event = its_get_event_id(d);
>> 
>> -    if (!irqd_is_forwarded_to_vcpu(d))
>> -        return NULL;
>> +        return dev_event_to_vlpi_map(its_dev, event);
>> +    }
>> 
>> -    return dev_event_to_vlpi_map(its_dev, event);
>> +    return NULL;
>>   }
>> 
>>   static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
>> 
>> 
>> Or am I missing the actual problem?
> 
> No. I also thought about fixing the issue by this way and I'm OK with
> both approaches.

OK, thanks. I've added this to irqchip-next[1], and rebased the v4.1
series on top of it. That way, the fix will trickle down to stable
without conflicts.

I've also given it a go on D05 with GICv4 enabled, and nothing caught 
fire.

         M.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/irqchip-next&id=093bf439fee0d40ade7e309c1288b409cdc3b38f
-- 
Jazz is not dead. It just smells funny...