Re: [PATCH v2 06/17] irqchip/gic-v3: Configure SGIs as standard interrupts

From: Valentin Schneider
Date: Thu Jun 25 2020 - 14:25:52 EST



On 24/06/20 20:58, Marc Zyngier wrote:
> Change the way we deal with GICv3 SGIs by turning them into proper
> IRQs, and calling into the arch code to register the interrupt range
> instead of a callback.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> drivers/irqchip/irq-gic-v3.c | 81 +++++++++++++++++++-----------------
> 1 file changed, 43 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 19b294ed48ba..d275e9b9533d 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -36,6 +36,8 @@
> #define FLAGS_WORKAROUND_GICR_WAKER_MSM8996 (1ULL << 0)
> #define FLAGS_WORKAROUND_CAVIUM_ERRATUM_38539 (1ULL << 1)
>
> +#define GIC_IRQ_TYPE_PARTITION (GIC_IRQ_TYPE_LPI + 1)
> +

Nit: this piqued my interest but ended up being just a define shuffle; As a
member of the git speleologists' guild, I'd be overjoyed with having a
small notion of that in the changelog.

> struct redist_region {
> void __iomem *redist_base;
> phys_addr_t phys_base;
> @@ -657,38 +659,14 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
> if ((irqnr >= 1020 && irqnr <= 1023))
> return;
>
> - /* Treat anything but SGIs in a uniform way */
> - if (likely(irqnr > 15)) {
> - int err;
> -
> - if (static_branch_likely(&supports_deactivate_key))
> - gic_write_eoir(irqnr);
> - else
> - isb();
> -
> - err = handle_domain_irq(gic_data.domain, irqnr, regs);
> - if (err) {
> - WARN_ONCE(true, "Unexpected interrupt received!\n");
> - gic_deactivate_unhandled(irqnr);
> - }
> - return;
> - }
> - if (irqnr < 16) {
> + if (static_branch_likely(&supports_deactivate_key))
> gic_write_eoir(irqnr);
> - if (static_branch_likely(&supports_deactivate_key))
> - gic_write_dir(irqnr);
> -#ifdef CONFIG_SMP
> - /*
> - * Unlike GICv2, we don't need an smp_rmb() here.
> - * The control dependency from gic_read_iar to
> - * the ISB in gic_write_eoir is enough to ensure
> - * that any shared data read by handle_IPI will
> - * be read after the ACK.
> - */

Isn't that still relevant?

Also, while staring at this it dawned on me that IPI's don't need the
eoimode=0 isb(): due to how the IPI flow-handler is structured, we'll get a
gic_eoi_irq() just before calling into the irqaction. Dunno how much we
care about it.

> - handle_IPI(irqnr, regs);
> -#else
> - WARN_ONCE(true, "Unexpected SGI received!\n");
> -#endif
> + else
> + isb();
> +
> + if (handle_domain_irq(gic_data.domain, irqnr, regs)) {
> + WARN_ONCE(true, "Unexpected interrupt received!\n");
> + gic_deactivate_unhandled(irqnr);
> }
> }
>