On Thu, Nov 26, 2020 at 04:08:57PM +0100, Niklas Schnelle wrote:
>
>
> On 11/26/20 1:19 PM, Alexander Gordeev 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 is not necessarily matches the kernel logical CPU
> > number.
>
> I took the liberty of correcting the "is not" grammar error
> above to "does not necessarily match".
>
> >
> > Fixes: e979ce7bced2 ("s390/pci: provide support for CPU directed interrupts")
> > Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
>
> Still works well and checkpatches clean. I
>
> > ---
> > arch/s390/pci/pci_irq.c | 15 ++++++++++++---
> > 1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
> > index 743f257cf2cb..1309fd302f58 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 +289,16 @@ 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);
> > + cpu_addr = smp_cpu_get_cpu_address(cpu);
> > + } else {
> > + cpu_addr = 0;
> > + }
>
> One question I haven't really figured out from looking at the spec is
> why using cpu_addr = 0; is a good fallback. Shouldn't that be smp_cpu_get_cpu_address(0) or
> do we now know that the CPU addresses always start at 0?
Nice catch! I think the safest way is smp_cpu_get_cpu_address(0)
whatever the spec says. I'll send v3.
> > +
> > 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);
> > }
> >
