Re: [PATCH 2/6] irqchip/ls-scfg-msi: Fix MSI affinity handling

[Marc Zyngier]

On 19/06/18 13:00, Thomas Gleixner wrote:
> On Tue, 19 Jun 2018, Marc Zyngier wrote:
> 
>> The ls-scfs-msi driver is not dealing with the effective affinity
>> as it should. Let's fix that, and make it clear that the effective
>> affinity is restricted to a single CPU.
>>
>> Reported-by: Alexandre Belloni <alexandre.bell...@bootlin.com>
>> Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
>> ---
>>  drivers/irqchip/irq-ls-scfg-msi.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-ls-scfg-msi.c 
>> b/drivers/irqchip/irq-ls-scfg-msi.c
>> index 1ec3bfe56693..2811cc53e425 100644
>> --- a/drivers/irqchip/irq-ls-scfg-msi.c
>> +++ b/drivers/irqchip/irq-ls-scfg-msi.c
>> @@ -121,7 +121,8 @@ static int ls_scfg_msi_set_affinity(struct irq_data 
>> *irq_data,
>>              return -EINVAL;
>>      }
>>  
>> -    cpumask_copy(irq_data->common->affinity, mask);
>> +    cpumask_copy(irq_data->common->affinity, cpumask_of(cpu));
> 
> That's wrong. The driver should not fiddle with the affinity mask at all
> and just store the effective mask.

Ah, very good point. The ls_scfg_msi_compose_msg callback is also pretty
dodgy in that respect...

> 
>> +    irq_data_update_effective_affinity(irq_data, cpumask_of(cpu));
>>  
>>      return IRQ_SET_MASK_OK;
> 
> If yuo look at the call site, then you'll notice that it will do:
> 
>         case IRQ_SET_MASK_OK:
>         case IRQ_SET_MASK_OK_DONE:
>                 cpumask_copy(desc->irq_common_data.affinity, mask);
> 
> So the cpumask_copy() can just go away.

Thanks for noticing that. I've fixed it up as follow:

diff --git a/drivers/irqchip/irq-ls-scfg-msi.c 
b/drivers/irqchip/irq-ls-scfg-msi.c
index 2811cc53e425..c671b3212010 100644
--- a/drivers/irqchip/irq-ls-scfg-msi.c
+++ b/drivers/irqchip/irq-ls-scfg-msi.c
@@ -93,8 +93,12 @@ static void ls_scfg_msi_compose_msg(struct irq_data *data, 
struct msi_msg *msg)
        msg->address_lo = lower_32_bits(msi_data->msiir_addr);
        msg->data = data->hwirq;
 
-       if (msi_affinity_flag)
-               msg->data |= cpumask_first(data->common->affinity);
+       if (msi_affinity_flag) {
+               const struct cpumask *mask;
+
+               mask = irq_data_get_effective_affinity_mask(data);
+               msg->data |= cpumask_first(mask);
+       }
 
        iommu_dma_map_msi_msg(data->irq, msg);
 }
@@ -121,7 +125,6 @@ static int ls_scfg_msi_set_affinity(struct irq_data 
*irq_data,
                return -EINVAL;
        }
 
-       cpumask_copy(irq_data->common->affinity, cpumask_of(cpu));
        irq_data_update_effective_affinity(irq_data, cpumask_of(cpu));
 
        return IRQ_SET_MASK_OK;

Thanks,

        M.
-- 
Jazz is not dead. It just smells funny...