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Date: Tue, 14 Dec 2021 11:40:57 +0000
From: Marc Zyngier <maz@...nel.org>
To: Sunil Muthuswamy <sunilmut@...rosoft.com>
Cc: KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
Dexuan Cui <decui@...rosoft.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
"lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
"robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"arnd@...db.de" <arnd@...db.de>, "x86@...nel.org" <x86@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH v6 2/2] arm64: PCI: hv: Add support for Hyper-V vPCI
On Tue, 14 Dec 2021 00:46:59 +0000,
Sunil Muthuswamy <sunilmut@...rosoft.com> wrote:
>
> On Friday, November 19, 2021 7:47 AM,
> Marc Zyngier <maz@...nel.org> wrote:
>
> [nip..]
>
> > > +static int hv_pci_vec_alloc_device_irq(struct irq_domain *domain,
> > > + unsigned int nr_irqs,
> > > + irq_hw_number_t *hwirq)
> > > +{
> > > + struct hv_pci_chip_data *chip_data = domain->host_data;
> > > + unsigned int index;
> > > +
> > > + /* Find and allocate region from the SPI bitmap */
> > > + mutex_lock(&chip_data->map_lock);
> > > + index = bitmap_find_free_region(chip_data->spi_map,
> > > + HV_PCI_MSI_SPI_NR,
> > > + get_count_order(nr_irqs));
> > > + mutex_unlock(&chip_data->map_lock);
> > > + if (index < 0)
> > > + return -ENOSPC;
> > > +
> > > + *hwirq = index + HV_PCI_MSI_SPI_START;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int hv_pci_vec_irq_gic_domain_alloc(struct irq_domain *domain,
> > > + unsigned int virq,
> > > + irq_hw_number_t hwirq)
> > > +{
> > > + struct irq_fwspec fwspec;
> > > +
> > > + fwspec.fwnode = domain->parent->fwnode;
> > > + fwspec.param_count = 2;
> > > + fwspec.param[0] = hwirq;
> > > + fwspec.param[1] = IRQ_TYPE_EDGE_RISING;
> > > +
> > > + return irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
> >
> > I think you are missing the actual edge configuration here. Since the
> > interrupt specifier doesn't come from either DT or ACPI, nobody will
> > set the trigger type, and you have to do it yourself here. At the
> > moment, you will get whatever is in the GIC configuration.
> >
>
> I see, thanks. So, just a call of irq_set_irq_type(IRQ_TYPE_EDGE_RISING)?
You are already deep in the irq stack, and calling a high level
function here is a pretty bad idea. You'll need something like:
struct irq_data *d;
d = irq_domain_get_irq_data(domain->parent, virq);
d->chip->irq_set_type(d, IRQ_TYPE_EDGE_RISING);
on the return from the parent allocation.
> > > +}
> > > +
> > > +static int hv_pci_vec_irq_domain_alloc(struct irq_domain *domain,
> > > + unsigned int virq, unsigned int nr_irqs,
> > > + void *args)
> > > +{
> > > + irq_hw_number_t hwirq;
> > > + unsigned int i;
> > > + int ret;
> > > +
> > > + ret = hv_pci_vec_alloc_device_irq(domain, nr_irqs, &hwirq);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + for (i = 0; i < nr_irqs; i++) {
> > > + ret = hv_pci_vec_irq_gic_domain_alloc(domain, virq + i,
> > > + hwirq + i);
> > > + if (ret)
> > > + goto free_irq;
> > > +
> > > + ret = irq_domain_set_hwirq_and_chip(domain, virq + i,
> > > + hwirq + i,
> > > + &hv_arm64_msi_irq_chip,
> > > + domain->host_data);
> > > + if (ret)
> > > + goto free_irq;
> > > +
> > > + pr_debug("pID:%d vID:%u\n", (int)(hwirq + i), virq + i);
> > > + }
> > > +
> > > + return 0;
> > > +
> > > +free_irq:
> > > + hv_pci_vec_irq_domain_free(domain, virq, nr_irqs);
> > > +
> > > + return ret;
> >
> > How about the interrupts that have already been allocated?
>
> Not sure I am fully following. If you are referring to the failure
> path and the interrupts that were allocated, then I am calling '
> hv_pci_vec_irq_domain_free' which should free the interrupts from
> the bitmap and the parent irq domain. Can you please clarify?
I see several problems on the failure path:
- You are freeing more than you actually configured. Not necessary a
big deal, but still (it is a common issue, and the core deals with
it)
- hv_pci_vec_irq_domain_free() calls irq_domain_reset_irq_data() on a
single pointer. Why? Either you wipe them all, or you don't.
>
> >
> > > +}
> > > +
> > > +/*
> > > + * Pick the first online cpu as the irq affinity that can be temporarily used
> > > + * for composing MSI from the hypervisor. GIC will eventually set the right
> > > + * affinity for the irq and the 'unmask' will retarget the interrupt to that
> > > + * cpu.
> > > + */
> > > +static int hv_pci_vec_irq_domain_activate(struct irq_domain *domain,
> > > + struct irq_data *irqd, bool reserve)
> > > +{
> > > + int cpu = cpumask_first(cpu_online_mask);
> > > +
> > > + irq_data_update_effective_affinity(irqd, cpumask_of(cpu));
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static const struct irq_domain_ops hv_pci_domain_ops = {
> > > + .alloc = hv_pci_vec_irq_domain_alloc,
> > > + .free = hv_pci_vec_irq_domain_free,
> > > + .activate = hv_pci_vec_irq_domain_activate,
> > > +};
> > > +
> > > +static int hv_pci_irqchip_init(void)
> > > +{
> > > + static struct hv_pci_chip_data *chip_data;
> > > + struct fwnode_handle *fn = NULL;
> > > + int ret = -ENOMEM;
> > > +
> > > + chip_data = kzalloc(sizeof(*chip_data), GFP_KERNEL);
> > > + if (!chip_data)
> > > + return ret;
> > > +
> > > + mutex_init(&chip_data->map_lock);
> > > + fn = irq_domain_alloc_named_fwnode("Hyper-V ARM64 vPCI");
> >
> > This will appear in debugfs. I'd rather you keep it short, sweet and
> > without spaces. "hv_vpci_arm64" seems better to me.
>
> Sure, will fix in next version.
>
> > >
> > > @@ -1619,6 +1820,7 @@ static struct irq_chip hv_msi_irq_chip = {
> > > .irq_compose_msi_msg = hv_compose_msi_msg,
> > > .irq_set_affinity = irq_chip_set_affinity_parent,
> > > .irq_ack = irq_chip_ack_parent,
> > > + .irq_eoi = irq_chip_eoi_parent,
> > > .irq_mask = hv_irq_mask,
> > > .irq_unmask = hv_irq_unmask,
> >
> > You probably want to avoid unconditionally setting callbacks that may
> > have side effects on another architecture (ack on arm64, eoi on x86).
>
> Thanks. Will fix in next version.
>
> Is there some other feedback that would like to see get addressed in the
> current patch? Trying to close down on all remaining feedback items here.
Not at the moment, as I have paged this out a long time ago.
Addressing feedback more often than once a month would definitely
help. I usually complain about patches being sent too often, but
you're squarely in the opposite camp.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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