| Message ID | 20170923004207.22356-13-cdall@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 23/09/17 01:41, Christoffer Dall wrote: > It is currently unclear how to set the VCPU affinity for a percpu_devid > interrupt , since the Linux irq_data structure describes the state for > multiple interrupts, one for each physical CPU on the system. Since > each such interrupt can be associated with different VCPUs or none at > all, associating a single VCPU state with such an interrupt does not > capture the necessary semantics. > > The implementers of irq_set_affinity are the Intel and AMD IOMMUs, and > the ARM GIC irqchip. The Intel and AMD callers do not appear to use > percpu_devid interrupts, and the ARM GIC implementation only checks the > pointer against NULL vs. non-NULL. > > Therefore, simply update the function documentation to explain the > expected use in the context of percpu_devid interrupts, allowing future > changes or additions to irqchip implementers to do the right thing. > > This allows us to set the VCPU affinity for the virtual timer interrupt > in KVM/ARM, which is a percpu_devid (PPI) interrupt. > > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Marc Zyngier <marc.zyngier@arm.com> > Signed-off-by: Christoffer Dall <cdall@linaro.org> > --- > kernel/irq/manage.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > index 573dc52..2b2c94f 100644 > --- a/kernel/irq/manage.c > +++ b/kernel/irq/manage.c > @@ -381,7 +381,8 @@ int irq_select_affinity_usr(unsigned int irq) > /** > * irq_set_vcpu_affinity - Set vcpu affinity for the interrupt > * @irq: interrupt number to set affinity > - * @vcpu_info: vCPU specific data > + * @vcpu_info: vCPU specific data or pointer to a percpu array of vCPU > + * specific data for percpu_devid interrupts > * > * This function uses the vCPU specific data to set the vCPU > * affinity for an irq. The vCPU specific data is passed from > Acked-by: Marc Zyngier <marc.zyngier@arm.com> M.
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 573dc52..2b2c94f 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -381,7 +381,8 @@ int irq_select_affinity_usr(unsigned int irq) /** * irq_set_vcpu_affinity - Set vcpu affinity for the interrupt * @irq: interrupt number to set affinity - * @vcpu_info: vCPU specific data + * @vcpu_info: vCPU specific data or pointer to a percpu array of vCPU + * specific data for percpu_devid interrupts * * This function uses the vCPU specific data to set the vCPU * affinity for an irq. The vCPU specific data is passed from
It is currently unclear how to set the VCPU affinity for a percpu_devid interrupt , since the Linux irq_data structure describes the state for multiple interrupts, one for each physical CPU on the system. Since each such interrupt can be associated with different VCPUs or none at all, associating a single VCPU state with such an interrupt does not capture the necessary semantics. The implementers of irq_set_affinity are the Intel and AMD IOMMUs, and the ARM GIC irqchip. The Intel and AMD callers do not appear to use percpu_devid interrupts, and the ARM GIC implementation only checks the pointer against NULL vs. non-NULL. Therefore, simply update the function documentation to explain the expected use in the context of percpu_devid interrupts, allowing future changes or additions to irqchip implementers to do the right thing. This allows us to set the VCPU affinity for the virtual timer interrupt in KVM/ARM, which is a percpu_devid (PPI) interrupt. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Christoffer Dall <cdall@linaro.org> --- kernel/irq/manage.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)