Linux Virtualization - Jul 2020 - [PATCH V2 2/6] kvm: detect assigned device via irqbypass manager

On 2020/7/16 ??7:23, Zhu Lingshan wrote:
> vDPA devices has dedicated backed hardware like
> passthrough-ed devices. Then it is possible to setup irq
> offloading to vCPU for vDPA devices. Thus this patch tries to
> manipulated assigned device counters via irqbypass manager.

This part needs some tweak, e.g why assigned device could be detected 
through this way.

>
> We will increase/decrease the assigned device counter in kvm/x86.

And you need explain why we don't need similar thing in other arch.

Thanks

> Both vDPA and VFIO would go through this code path.
>
> This code path only affect x86 for now.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
> Suggested-by: Jason Wang <jasowang at redhat.com>
> ---
>   arch/x86/kvm/x86.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 00c88c2..20c07d3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10624,11 +10624,17 @@ int kvm_arch_irq_bypass_add_producer(struct
irq_bypass_consumer *cons,
>   {
>   	struct kvm_kernel_irqfd *irqfd >   		container_of(cons, struct
kvm_kernel_irqfd, consumer);
> +	int ret;
>   
>   	irqfd->producer = prod;
> +	kvm_arch_start_assignment(irqfd->kvm);
> +	ret = kvm_x86_ops.update_pi_irte(irqfd->kvm,
> +					 prod->irq, irqfd->gsi, 1);
> +
> +	if (ret)
> +		kvm_arch_end_assignment(irqfd->kvm);
>   
> -	return kvm_x86_ops.update_pi_irte(irqfd->kvm,
> -					   prod->irq, irqfd->gsi, 1);
> +	return ret;
>   }
>   
>   void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,