Linux Virtualization - Jul 2020 - [PATCH 2/7] kvm/vfio: detect assigned device via irqbypass manager

On Sun, 12 Jul 2020 22:49:21 +0800
Zhu Lingshan <lingshan.zhu at intel.com> wrote:
> We used to detect assigned device via VFIO manipulated device
> conters. This is less flexible consider VFIO is not the only
> interface for assigned device. vDPA devices has dedicated
> backed hardware as well. So this patch tries to detect
> the assigned device via irqbypass manager.
> 
> We will increase/decrease the assigned device counter in kvm/x86.
> Both vDPA and VFIO would go through this code path.
> 
> This code path only affect x86 for now.
No it doesn't, it only adds VFIO support to x86, but it removes it from
architecture neutral code.  Also a VFIO device does not necessarily
make use of the irqbypass manager, this depends on platform support and
enablement of this feature.   Therefore, NAK.  Thanks,

Alex
 
> Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
> ---
>  arch/x86/kvm/x86.c | 10 ++++++++--
>  virt/kvm/vfio.c    |  2 --
>  2 files changed, 8 insertions(+), 4 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,
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index 8fcbc50..111da52 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -226,7 +226,6 @@ static int kvm_vfio_set_group(struct kvm_device *dev,
long attr, u64 arg)
>  		list_add_tail(&kvg->node, &kv->group_list);
>  		kvg->vfio_group = vfio_group;
>  
> -		kvm_arch_start_assignment(dev->kvm);
>  
>  		mutex_unlock(&kv->lock);
>  
> @@ -254,7 +253,6 @@ static int kvm_vfio_set_group(struct kvm_device *dev,
long attr, u64 arg)
>  				continue;
>  
>  			list_del(&kvg->node);
> -			kvm_arch_end_assignment(dev->kvm);
>  #ifdef CONFIG_SPAPR_TCE_IOMMU
>  			kvm_spapr_tce_release_vfio_group(dev->kvm,
>  							 kvg->vfio_group);

On 2020/7/12 ??11:29, Alex Williamson wrote:
> On Sun, 12 Jul 2020 22:49:21 +0800
> Zhu Lingshan <lingshan.zhu at intel.com> wrote:
>
>> We used to detect assigned device via VFIO manipulated device
>> conters. This is less flexible consider VFIO is not the only
>> interface for assigned device. vDPA devices has dedicated
>> backed hardware as well. So this patch tries to detect
>> the assigned device via irqbypass manager.
>>
>> We will increase/decrease the assigned device counter in kvm/x86.
>> Both vDPA and VFIO would go through this code path.
>>
>> This code path only affect x86 for now.
> No it doesn't, it only adds VFIO support to x86, but it removes it from
> architecture neutral code.

Do you mean we should introduce a kvm_irq_bypass_add_producer and do 
kvm_arch_start_assignment( ) there?

> Also a VFIO device does not necessarily
> make use of the irqbypass manager, this depends on platform support and
> enablement of this feature.

Yes, we should keep the VFIO part unchanged.

Thanks

>    Therefore, NAK.  Thanks,
>
> Alex
>   
>> Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
>> ---
>>   arch/x86/kvm/x86.c | 10 ++++++++--
>>   virt/kvm/vfio.c    |  2 --
>>   2 files changed, 8 insertions(+), 4 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,
>> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
>> index 8fcbc50..111da52 100644
>> --- a/virt/kvm/vfio.c
>> +++ b/virt/kvm/vfio.c
>> @@ -226,7 +226,6 @@ static int kvm_vfio_set_group(struct kvm_device
*dev, long attr, u64 arg)
>>   		list_add_tail(&kvg->node, &kv->group_list);
>>   		kvg->vfio_group = vfio_group;
>>   
>> -		kvm_arch_start_assignment(dev->kvm);
>>   
>>   		mutex_unlock(&kv->lock);
>>   
>> @@ -254,7 +253,6 @@ static int kvm_vfio_set_group(struct kvm_device
*dev, long attr, u64 arg)
>>   				continue;
>>   
>>   			list_del(&kvg->node);
>> -			kvm_arch_end_assignment(dev->kvm);
>>   #ifdef CONFIG_SPAPR_TCE_IOMMU
>>   			kvm_spapr_tce_release_vfio_group(dev->kvm,
>>   							 kvg->vfio_group);