Re: [Qemu-devel] [RFC v2 2/3] intc/arm_gic: Support IRQ injection for more than 256 vpus

[Andrew Jones]

On Wed, Sep 11, 2019 at 05:51:24PM +0200, Eric Auger wrote:
> Host kernels that expose the KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 capability
> allow injection of interrupts along with vcpu ids larger than 255.
> Let's encode the vpcu id on 12 bits according to the upgraded KVM_IRQ_LINE
> ABI when needed.
> 
> Given that we have two callsites that need to assemble
> the value for kvm_set_irq(), a new helper routine, kvm_arm_set_irq
> is introduced.
> 
> Without that patch qemu exits with "kvm_set_irq: Invalid argument"
> message.
> 
> Signed-off-by: Eric Auger <address@hidden>
> Reported-by: Zenghui Yu <address@hidden>
> ---
>  hw/intc/arm_gic_kvm.c |  7 ++-----
>  target/arm/cpu.c      | 10 ++++------
>  target/arm/kvm.c      | 16 ++++++++++++++++
>  target/arm/kvm_arm.h  |  1 +
>  4 files changed, 23 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/intc/arm_gic_kvm.c b/hw/intc/arm_gic_kvm.c
> index b56fda144f..9deb15e7e6 100644
> --- a/hw/intc/arm_gic_kvm.c
> +++ b/hw/intc/arm_gic_kvm.c
> @@ -55,7 +55,7 @@ void kvm_arm_gic_set_irq(uint32_t num_irq, int irq, int 
> level)
>       * has separate fields in the irq number for type,
>       * CPU number and interrupt number.
>       */
> -    int kvm_irq, irqtype, cpu;
> +    int irqtype, cpu;
>  
>      if (irq < (num_irq - GIC_INTERNAL)) {
>          /* External interrupt. The kernel numbers these like the GIC
> @@ -72,10 +72,7 @@ void kvm_arm_gic_set_irq(uint32_t num_irq, int irq, int 
> level)
>          cpu = irq / GIC_INTERNAL;
>          irq %= GIC_INTERNAL;
>      }
> -    kvm_irq = (irqtype << KVM_ARM_IRQ_TYPE_SHIFT)
> -        | (cpu << KVM_ARM_IRQ_VCPU_SHIFT) | irq;
> -
> -    kvm_set_irq(kvm_state, kvm_irq, !!level);
> +    kvm_arm_set_irq(cpu, irqtype, irq, !!level);
>  }
>  
>  static void kvm_arm_gicv2_set_irq(void *opaque, int irq, int level)
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 2399c14471..13813fb213 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -576,16 +576,16 @@ static void arm_cpu_kvm_set_irq(void *opaque, int irq, 
> int level)
>      ARMCPU *cpu = opaque;
>      CPUARMState *env = &cpu->env;
>      CPUState *cs = CPU(cpu);
> -    int kvm_irq = KVM_ARM_IRQ_TYPE_CPU << KVM_ARM_IRQ_TYPE_SHIFT;
>      uint32_t linestate_bit;
> +    int irq_id;
>  
>      switch (irq) {
>      case ARM_CPU_IRQ:
> -        kvm_irq |= KVM_ARM_IRQ_CPU_IRQ;
> +        irq_id = KVM_ARM_IRQ_CPU_IRQ;
>          linestate_bit = CPU_INTERRUPT_HARD;
>          break;
>      case ARM_CPU_FIQ:
> -        kvm_irq |= KVM_ARM_IRQ_CPU_FIQ;
> +        irq_id = KVM_ARM_IRQ_CPU_FIQ;
>          linestate_bit = CPU_INTERRUPT_FIQ;
>          break;
>      default:
> @@ -597,9 +597,7 @@ static void arm_cpu_kvm_set_irq(void *opaque, int irq, 
> int level)
>      } else {
>          env->irq_line_state &= ~linestate_bit;
>      }
> -
> -    kvm_irq |= cs->cpu_index << KVM_ARM_IRQ_VCPU_SHIFT;
> -    kvm_set_irq(kvm_state, kvm_irq, level ? 1 : 0);
> +    kvm_arm_set_irq(cs->cpu_index, KVM_ARM_IRQ_TYPE_CPU, irq_id, !!level);
>  #endif
>  }
>  
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index b2eaa50b8d..6cdfa2204f 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -744,6 +744,22 @@ int kvm_arm_vgic_probe(void)
>      }
>  }
>  
> +int kvm_arm_set_irq(int cpu, int irqtype, int irq, int level)
> +{
> +    int kvm_irq = 0;

No need to init to zero, and could just immediately init with the
line below instead.

> +
> +    kvm_irq = (irqtype << KVM_ARM_IRQ_TYPE_SHIFT) | irq;
> +
> +    if (cpu != 0) {

No need for this 'if'

> +        int cpu_idx2 = cpu / 256;
> +        int cpu_idx1 = cpu % 256;
> +
> +        kvm_irq |= (cpu_idx1 << KVM_ARM_IRQ_VCPU_SHIFT) |
> +           ((cpu_idx2 & KVM_ARM_IRQ_VCPU2_MASK) << KVM_ARM_IRQ_VCPU2_SHIFT);

Masking should be unnecessary as the only way it'll do anything is if we
have vcpus >= 4096, which I imagine will never happen or will be guarded
against happening elsewhere. Silently masking doesn't look right anyway,
so I'd either add an assert(cpu_idx2 < 16) and drop the masking or just
drop the masking.

> +    }
> +    return kvm_set_irq(kvm_state, kvm_irq, !!level);
> +}
> +
>  int kvm_arch_fixup_msi_route(struct kvm_irq_routing_entry *route,
>                               uint64_t address, uint32_t data, PCIDevice *dev)
>  {
> diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> index b3106c8600..b4e19457a0 100644
> --- a/target/arm/kvm_arm.h
> +++ b/target/arm/kvm_arm.h
> @@ -253,6 +253,7 @@ int kvm_arm_vgic_probe(void);
>  
>  void kvm_arm_pmu_set_irq(CPUState *cs, int irq);
>  void kvm_arm_pmu_init(CPUState *cs);
> +int kvm_arm_set_irq(int cpu, int irqtype, int irq, int level);
>  
>  #else
>  
> -- 
> 2.20.1
> 
>

Thanks,
drew