Re: [PATCH V2] genirq/affinity: Handle affinity setting on inactive interrupts correctly

From: Marc Zyngier
Date: Sat Jul 25 2020 - 08:31:08 EST

Hi Thomas,

On Fri, 24 Jul 2020 21:44:41 +0100,
Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> John,
>
> Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes:
> > I have some ideas for a trivial generic way to solve this without
> > undoing the commit in question and without going through all the irq
> > chip drivers. So far everything I came up with is butt ugly. Maybe Marc
> > has some brilliant idea.
> >
> > Sorry for the wreckage and thanks for the excellent problem
> > description. I'll come back to you in the next days.
>
> couldn't give up :)
>
> So after staring in too many drivers, I resorted to make this mode
> opt-in and mark the interrupts accordingly for the two drivers which are
> known to want this. Not that I love it, but it's the least dangerous
> option. Completely untested patch below.
>
> Thanks,
>
> tglx
> ---
> arch/x86/kernel/apic/vector.c | 4 ++++
> drivers/irqchip/irq-gic-v3-its.c | 5 ++++-
> include/linux/irq.h | 13 +++++++++++++
> kernel/irq/manage.c | 6 +++++-
> 4 files changed, 26 insertions(+), 2 deletions(-)
>
> --- a/arch/x86/kernel/apic/vector.c
> +++ b/arch/x86/kernel/apic/vector.c
> @@ -560,6 +560,10 @@ static int x86_vector_alloc_irqs(struct
> * as that can corrupt the affinity move state.
> */
> irqd_set_handle_enforce_irqctx(irqd);
> +
> + /* Don't invoke affinity setter on deactivated interrupts */
> + irqd_set_affinity_on_activate(irqd);
> +
> /*
> * Legacy vectors are already assigned when the IOAPIC
> * takes them over. They stay on the same vector. This is
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -3523,6 +3523,7 @@ static int its_irq_domain_alloc(struct i
> msi_alloc_info_t *info = args;
> struct its_device *its_dev = info->scratchpad[0].ptr;
> struct its_node *its = its_dev->its;
> + struct irq_data *irqd;
> irq_hw_number_t hwirq;
> int err;
> int i;
> @@ -3542,7 +3543,9 @@ static int its_irq_domain_alloc(struct i
>
> irq_domain_set_hwirq_and_chip(domain, virq + i,
> hwirq + i, &its_irq_chip, its_dev);
> - irqd_set_single_target(irq_desc_get_irq_data(irq_to_desc(virq + i)));
> + irqd = irq_get_irq_data(virq + i);
> + irqd_set_single_target(irqd);
> + irqd_set_affinity_on_activate(irqd);
> pr_debug("ID:%d pID:%d vID:%d\n",
> (int)(hwirq + i - its_dev->event_map.lpi_base),
> (int)(hwirq + i), virq + i);
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -213,6 +213,8 @@ struct irq_data {
> * required
> * IRQD_HANDLE_ENFORCE_IRQCTX - Enforce that handle_irq_*() is only invoked
> * from actual interrupt context.
> + * IRQD_AFFINITY_ON_ACTIVATE - Affinity is set on activation. Don't call
> + * irq_chip::irq_set_affinity() when deactivated.
> */
> enum {
> IRQD_TRIGGER_MASK = 0xf,
> @@ -237,6 +239,7 @@ enum {
> IRQD_CAN_RESERVE = (1 << 26),
> IRQD_MSI_NOMASK_QUIRK = (1 << 27),
> IRQD_HANDLE_ENFORCE_IRQCTX = (1 << 28),
> + IRQD_AFFINITY_ON_ACTIVATE = (1 << 29),
> };
>
> #define __irqd_to_state(d) ACCESS_PRIVATE((d)->common, state_use_accessors)
> @@ -421,6 +424,16 @@ static inline bool irqd_msi_nomask_quirk
> return __irqd_to_state(d) & IRQD_MSI_NOMASK_QUIRK;
> }
>
> +static inline void irqd_set_affinity_on_activate(struct irq_data *d)
> +{
> + __irqd_to_state(d) |= IRQD_AFFINITY_ON_ACTIVATE;
> +}
> +
> +static inline bool irqd_affinity_on_activate(struct irq_data *d)
> +{
> + return __irqd_to_state(d) & IRQD_AFFINITY_ON_ACTIVATE;
> +}
> +
> #undef __irqd_to_state
>
> static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -320,12 +320,16 @@ static bool irq_set_affinity_deactivated
> struct irq_desc *desc = irq_data_to_desc(data);
>
> /*
> + * Handle irq chips which can handle affinity only in activated
> + * state correctly
> + *
> * If the interrupt is not yet activated, just store the affinity
> * mask and do not call the chip driver at all. On activation the
> * driver has to make sure anyway that the interrupt is in a
> * useable state so startup works.
> */
> - if (!IS_ENABLED(CONFIG_IRQ_DOMAIN_HIERARCHY) || irqd_is_activated(data))
> + if (!IS_ENABLED(CONFIG_IRQ_DOMAIN_HIERARCHY) ||
> + irqd_is_activated(data) || !irqd_affinity_on_activate(data))
> return false;
>
> cpumask_copy(desc->irq_common_data.affinity, mask);
>

I have given this a go on two systems: one with a GICv2 that has its
PMUs wired in a similar way to John's system (each CPU PMU is on a
separate SPI), and another one that has an ITS. Both came up normally
and their interrupts are routed as expected:

* GICv2 PMU:
30: 121 0 0 0 0 0 0 0 GICv2 39 Level arm-pmu
31: 0 167 0 0 0 0 0 0 GICv2 40 Level arm-pmu
32: 0 0 145 0 0 0 0 0 GICv2 41 Level arm-pmu
33: 0 0 0 400 0 0 0 0 GICv2 42 Level arm-pmu
34: 0 0 0 0 97 0 0 0 GICv2 43 Level arm-pmu
35: 0 0 0 0 0 463 0 0 GICv2 44 Level arm-pmu
36: 0 0 0 0 0 0 74 0 GICv2 45 Level arm-pmu
37: 0 0 0 0 0 0 0 8 GICv2 46 Level arm-pmu

* GICv3+ITS:
241: 219 0 0 0 0 0 ITS-MSI 524289 Edge nvme0q1
242: 0 251 0 0 0 0 ITS-MSI 524290 Edge nvme0q2
243: 0 0 197 0 0 0 ITS-MSI 524291 Edge nvme0q3
244: 0 0 0 380 0 0 ITS-MSI 524292 Edge nvme0q4
245: 0 0 0 0 675 0 ITS-MSI 524293 Edge nvme0q5
246: 0 0 0 0 0 436 ITS-MSI 524294 Edge nvme0q6

For a good measure, I've added this on top, adding the missing bits to
the debugfs entries:

diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index 4f9f844074db..d44fc8a5dab2 100644
--- a/kernel/irq/debugfs.c
+++ b/kernel/irq/debugfs.c
@@ -120,6 +120,9 @@ static const struct irq_bit_descr irqdata_states[] = {

BIT_MASK_DESCR(IRQD_WAKEUP_STATE),
BIT_MASK_DESCR(IRQD_WAKEUP_ARMED),
+ BIT_MASK_DESCR(IRQD_DEFAULT_TRIGGER_SET),
+ BIT_MASK_DESCR(IRQD_HANDLE_ENFORCE_IRQCTX),
+ BIT_MASK_DESCR(IRQD_AFFINITY_ON_ACTIVATE),
};

static const struct irq_bit_descr irqdesc_states[] = {

FWIW:

Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
Tested-by: Marc Zyngier <maz@xxxxxxxxxx>


M.

--
Without deviation from the norm, progress is not possible.