[PATCH v1 0/2] irqchip/gic-v3-its: don't set bitmap for LPI which user didn't allocate

[PATCH v1 0/2] irqchip/gic-v3-its: don't set bitmap for LPI which user didn't allocate

[Luo Jiaxing]

When the number of online CPUs is less than 16, we found that it will fail
to allocate 32 MSI interrupts (including 16 affinity interrupts) after the
hisi_sas module is unloaded and then reloaded.

After analysis, it is found that a bug exists when the ITS releases
interrupt resources, and this patch set contains a bugfix patch and a patch
for appending debugging information.

Luo Jiaxing (2):
  irqchip/gic-v3-its: don't set bitmap for LPI which user didn't
    allocate
  genirq/msi: add an error print when __irq_domain_alloc_irqs() failed

 drivers/irqchip/irq-gic-v3-its.c | 4 ++++
 kernel/irq/msi.c                 | 1 +
 2 files changed, 5 insertions(+)

-- 
2.7.4

[PATCH v1 1/2] irqchip/gic-v3-its: don't set bitmap for LPI which user didn't allocate

[Luo Jiaxing]

The driver sets the LPI bitmap of device based on get_count_order(nvecs).
This means that when the number of LPI interrupts does not meet the power
of two, redundant bits are set in the LPI bitmap. However, when free
interrupt, these redundant bits is not cleared. As a result, device will
fails to allocate the same numbers of interrupts next time.

Therefore, clear the redundant bits set in LPI bitmap.

Fixes: 4615fbc3788d ("genirq/irqdomain: Don't try to free an interrupt that has no mapping")

Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index ed46e60..027f7ef 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3435,6 +3435,10 @@ static int its_alloc_device_irq(struct its_device *dev, int nvecs, irq_hw_number
 
 	*hwirq = dev->event_map.lpi_base + idx;
 
+	bitmap_clear(dev->event_map.lpi_map,
+		     idx + nvecs,
+		     roundup_pow_of_two(nvecs) - nvecs);
+
 	return 0;
 }
 
-- 
2.7.4

[PATCH v1 2/2] genirq/msi: add an error print when __irq_domain_alloc_irqs() failed

[Luo Jiaxing]

During debug, we found that the return value of __irq_domain_alloc_irqs()
will be overwritten by the return value of subsequent function. As a
result, the locating clue will be lost.

To improve debug efficiency, an error message is added to print the
return value of __irq_domain_alloc_irqs().

Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
---
 kernel/irq/msi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index b338d62..f8729b0 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -418,6 +418,7 @@ int __msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 					       desc->affinity);
 		if (virq < 0) {
 			ret = -ENOSPC;
+			dev_err(dev, "failed to allocate irq, virq=%d\n", virq);
 			if (ops->handle_error)
 				ret = ops->handle_error(domain, desc, ret);
 			if (ops->msi_finish)
-- 
2.7.4

Re: [Linuxarm] [PATCH v1 0/2] irqchip/gic-v3-its: don't set bitmap for LPI which user didn't allocate

[John Garry]

On 08/02/2021 10:58, Luo Jiaxing wrote:
> When the number of online CPUs is less than 16, we found that it will fail
> to allocate 32 MSI interrupts (including 16 affinity interrupts) after the
> hisi_sas module is unloaded and then reloaded.
> 
> After analysis, it is found that a bug exists when the ITS releases
> interrupt resources, and this patch set contains a bugfix patch and a patch
> for appending debugging information.

Please note that this issue has already been reported:
https://lore.kernel.org/lkml/fd88ce05-8aee-5b1f-5ab6-be88fa53d3aa@huawei.com/

> 
> Luo Jiaxing (2):
>    irqchip/gic-v3-its: don't set bitmap for LPI which user didn't
>      allocate
>    genirq/msi: add an error print when __irq_domain_alloc_irqs() failed
> 
>   drivers/irqchip/irq-gic-v3-its.c | 4 ++++
>   kernel/irq/msi.c                 | 1 +
>   2 files changed, 5 insertions(+)
> 

Re: [PATCH v1 1/2] irqchip/gic-v3-its: don't set bitmap for LPI which user didn't allocate

[Marc Zyngier]

On 2021-02-08 10:58, Luo Jiaxing wrote:
> The driver sets the LPI bitmap of device based on 
> get_count_order(nvecs).
> This means that when the number of LPI interrupts does not meet the 
> power
> of two, redundant bits are set in the LPI bitmap. However, when free
> interrupt, these redundant bits is not cleared. As a result, device 
> will
> fails to allocate the same numbers of interrupts next time.
> 
> Therefore, clear the redundant bits set in LPI bitmap.
> 
> Fixes: 4615fbc3788d ("genirq/irqdomain: Don't try to free an interrupt
> that has no mapping")
> 
> Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> b/drivers/irqchip/irq-gic-v3-its.c
> index ed46e60..027f7ef 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -3435,6 +3435,10 @@ static int its_alloc_device_irq(struct
> its_device *dev, int nvecs, irq_hw_number
> 
>  	*hwirq = dev->event_map.lpi_base + idx;
> 
> +	bitmap_clear(dev->event_map.lpi_map,
> +		     idx + nvecs,
> +		     roundup_pow_of_two(nvecs) - nvecs);
> +
>  	return 0;
>  }

What makes you think that the remaining LPIs are free to be released?
Even if the end-point has request a non-po2 number of MSIs, it could
very well rely on the the rest of it to be available (specially in the
case of PCI Multi-MSI).

Have a look at the thread pointed out by John for a potential fix.

Thanks,

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

Re: [PATCH v1 1/2] irqchip/gic-v3-its: don't set bitmap for LPI which user didn't allocate

[luojiaxing]

On 2021/2/8 19:59, Marc Zyngier wrote:
> On 2021-02-08 10:58, Luo Jiaxing wrote:
>> The driver sets the LPI bitmap of device based on 
>> get_count_order(nvecs).
>> This means that when the number of LPI interrupts does not meet the 
>> power
>> of two, redundant bits are set in the LPI bitmap. However, when free
>> interrupt, these redundant bits is not cleared. As a result, device will
>> fails to allocate the same numbers of interrupts next time.
>>
>> Therefore, clear the redundant bits set in LPI bitmap.
>>
>> Fixes: 4615fbc3788d ("genirq/irqdomain: Don't try to free an interrupt
>> that has no mapping")
>>
>> Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
>> ---
>>  drivers/irqchip/irq-gic-v3-its.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
>> b/drivers/irqchip/irq-gic-v3-its.c
>> index ed46e60..027f7ef 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -3435,6 +3435,10 @@ static int its_alloc_device_irq(struct
>> its_device *dev, int nvecs, irq_hw_number
>>
>>      *hwirq = dev->event_map.lpi_base + idx;
>>
>> +    bitmap_clear(dev->event_map.lpi_map,
>> +             idx + nvecs,
>> +             roundup_pow_of_two(nvecs) - nvecs);
>> +
>>      return 0;
>>  }
>
> What makes you think that the remaining LPIs are free to be released?


I think that the LPI bitmap is used to mark the valid LPI interrupts 
allocated to the PCIe device.

Therefore, for the remaining LPIs, the ITS can reserve entries in the 
ITT table, but the bitmap does not need to be set.


Maybe my understanding is wrong, and I'm a little confused about the 
function of this bitmap.


> Even if the end-point has request a non-po2 number of MSIs, it could
> very well rely on the the rest of it to be available (specially in the
> case of PCI Multi-MSI).


yes, you are right. But for Multi-MSI, does it mean that one PCIE device 
can own several MSI interrupts?


Another question, is it possible for module driver to use these 
remaining LPIs?

For example, in my case


I allcoate 32 MSI with 16 affi-IRQ in it.

MSI can only offer 20 MSIs because online CPU number is 4 and it create 
20 msi desc then.

ITS create a its device for this PCIe device and generate a ITT tabel 
for 32 MSIs.


so in MSI, it provide 20 valid MSIs, but in ITS, lpi bitmap show that 32 
MSI is allocated.

This logic is a bit strange and a little incomprehensible.


>
> Have a look at the thread pointed out by John for a potential fix.


Sorry for missing that, I think it can fix my issue too, let me test it 
later.


Thanks

jiaxing


>
> Thanks,
>
>         M.