Re: [PATCH v3] s390/pci: fix CPU address in MSI for directed IRQ

Niklas Schnelle
2020-11-27T10:09:31Z

On 11/27/20 9:56 AM, Halil Pasic wrote:
> On Thu, 26 Nov 2020 18:00:37 +0100
> Alexander Gordeev <agordeev@linux.ibm.com> wrote:
>
>> The directed MSIs are delivered to CPUs whose address is
>> written to the MSI message data. The current code assumes
>> that a CPU logical number (as it is seen by the kernel)
>> is also that CPU address.
>>
>> The above assumption is not correct, as the CPU address
>> is rather the value returned by STAP instruction. That
>> value does not necessarily match the kernel logical CPU
>> number.
>>
>> Fixes: e979ce7bced2 ("s390/pci: provide support for CPU directed interrupts")
>> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
>> ---
>> arch/s390/pci/pci_irq.c | 14 +++++++++++---
>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
>> index 743f257cf2cb..75217fb63d7b 100644
>> --- a/arch/s390/pci/pci_irq.c
>> +++ b/arch/s390/pci/pci_irq.c
>> @@ -103,9 +103,10 @@ static int zpci_set_irq_affinity(struct irq_data *data, const struct cpumask *de
>> {
>> struct msi_desc *entry = irq_get_msi_desc(data->irq);
>> struct msi_msg msg = entry->msg;
>> + int cpu_addr = smp_cpu_get_cpu_address(cpumask_first(dest));
>>
>> msg.address_lo &= 0xff0000ff;
>> - msg.address_lo |= (cpumask_first(dest) << 8);
>> + msg.address_lo |= (cpu_addr << 8);
>> pci_write_msi_msg(data->irq, &msg);
>>
>> return IRQ_SET_MASK_OK;
>> @@ -238,6 +239,7 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
>> unsigned long bit;
>> struct msi_desc *msi;
>> struct msi_msg msg;
>> + int cpu_addr;
>> int rc, irq;
>>
>> zdev->aisb = -1UL;
>> @@ -287,9 +289,15 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
>> handle_percpu_irq);
>> msg.data = hwirq - bit;
>> if (irq_delivery == DIRECTED) {
>> + if (msi->affinity)
>> + cpu = cpumask_first(&msi->affinity->mask);
>> + else
>> + cpu = 0;
>> + cpu_addr = smp_cpu_get_cpu_address(cpu);
>> +
>
> I thin style wise, I would prefer keeping the ternary operator instead
> of rewriting it as an if-then-else, i.e.:
> cpu_addr = smp_cpu_get_cpu_address(msi->affinity ?
> cpumask_first(&msi->affinity->mask) : 0);
> but either way:
>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>

Thanks for your review, lets keep the if/else its certainly not less
readable even if it may be less pretty.

Found another thing (not directly in the touched code) but I'm now
wondering about. In zpci_handle_cpu_local_irq()
we do
struct airq_iv *dibv = zpci_ibv[smp_processor_id()];

does that also need to use some _address() variant? If it does that
then dicatates that the CPU addresses must start at 0.

>
>> msg.address_lo = zdev->msi_addr & 0xff0000ff;
>> - msg.address_lo |= msi->affinity ?
>> - (cpumask_first(&msi->affinity->mask) << 8) : 0;
>> + msg.address_lo |= (cpu_addr << 8);
>> +
>> for_each_possible_cpu(cpu) {
>> airq_iv_set_data(zpci_ibv[cpu], hwirq, irq);
>> }
>