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Re: [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper functions

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On Mon, 30 Nov 2015, Qais Yousef wrote:
> On 11/30/2015 11:20 AM, Thomas Gleixner wrote:
> > On Wed, 25 Nov 2015, Qais Yousef wrote:
> > > cpumask is limited to NR_CPUS. Introduce ipi_mask which allows us to
> > > address
> > > cpu range that is higher than NR_CPUS which is required for drivers to
> > > send
> > > IPIs for coprocessor that are outside Linux CPU range.
> > I have second thoughts on this.
> > 
> > cpumask is indeed limited to NR_CPUS or in case of CPUMASK_ON_STACK
> > limited to nr_cpu_ids.
> > 
> > But, that's not an issue for that coprocessor case. Let's assume you
> > have 16 Linux CPUs and 4 coprocessors. So you set the number of
> > possible cpus (NR_CPUS) to 20. That makes the cpumask sizeof 20.
> > 
> > The boot-process sets the number of available cpus to 16. So the
> > Linux side will never try to access anything beyond cpu15.
> > 
> > But you can spare that extra mask magic and simply use cpumask. Sorry
> > that I did not think about that earlier.
> > 
> > 
> Yes it would be much better to reuse it but wouldn't the runtime checks
> against nr_cpu_ids create problems especially when CPUMASK_ON_STACK is
> defined?

nr_cpu_ids == find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;

Thanks,

	tglx
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[PATCH v2 00/19] Implement generic IPI support mechanism Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper functions Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
    Re: [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper  functions Thomas Gleixner <tglx@linutronix.de> - 2015-11-30 12:30 +0100
      Re: [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper  functions Qais Yousef <qais.yousef@imgtec.com> - 2015-11-30 12:50 +0100
        Re: [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper  functions Thomas Gleixner <tglx@linutronix.de> - 2015-11-30 14:20 +0100
          Re: [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper  functions Qais Yousef <qais.yousef@imgtec.com> - 2015-11-30 15:00 +0100
  [PATCH v2 16/19] MIPS: Add generic SMP IPI support Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 01/19] genirq: Add new IRQ_DOMAIN_FLAGS_IPI Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 03/19] genirq: Add GENERIC_IRQ_IPI Kconfig symbol Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 19/19] irqchip/mips-gic: Add new DT property to reserve IPIs Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
    Re: [PATCH v2 19/19] irqchip/mips-gic: Add new DT property to  reserve IPIs Rob Herring <robh@kernel.org> - 2015-11-25 17:10 +0100
  [PATCH v2 14/19] irqchip/mips-gic: Use gic_vpes instead of NR_CPUS Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 09/19] genirq: Add a new function to get IPI reverse mapping Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
    Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse  mapping Qais Yousef <qais.yousef@imgtec.com> - 2015-11-27 12:50 +0100
      Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse  mapping Thomas Gleixner <tglx@linutronix.de> - 2015-11-30 11:50 +0100
        Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse  mapping Qais Yousef <qais.yousef@imgtec.com> - 2015-11-30 12:00 +0100
          Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse  mapping Thomas Gleixner <tglx@linutronix.de> - 2015-11-30 12:30 +0100
            Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse  mapping Qais Yousef <qais.yousef@imgtec.com> - 2015-11-30 13:00 +0100
              Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse  mapping Qais Yousef <qais.yousef@imgtec.com> - 2015-12-01 11:50 +0100
  [PATCH v2 02/19] genirq: Add DOMAIN_BUS_IPI Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 11/19] genirq: Implement ipi_send_{mask, single}() Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:10 +0100
  [PATCH v2 15/19] irqchip/mips-gic: Clear percpu_masks correctly when mapping Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 17/19] MIPS: Make smp CMP, CPS and MT use the new generic IPI functions Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 12/19] irqchip/mips-gic: Add a IPI hierarchy domain Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 08/19] genirq: Add a new generic IPI reservation code to irq core Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 07/19] genirq: Make irq_domain_alloc_descs() non static Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 10/19] genirq: Add a new irq_send_ipi() to irq_chip Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 06/19] genirq: Add struct ipi_mapping and its helper functions Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 05/19] genirq: Add struct ipi_mask to irq_data Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100
  [PATCH v2 13/19] irqchip/mips-gic: Add device hierarchy domain Qais Yousef <qais.yousef@imgtec.com> - 2015-11-25 13:20 +0100

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