Re: [PATCHv4 2/2] kvm: deliver msi interrupts from irq handler

[Gleb Natapov <gleb@redhat.com>]

On Wed, Oct 17, 2012 at 06:06:06PM +0200, Michael S. Tsirkin wrote:
> We can deliver certain interrupts, notably MSI,
> from atomic context.  Use kvm_set_irq_inatomic,
> to implement an irq handler for msi.
> 
> This reduces the pressure on scheduler in case
> where host and guest irq share a host cpu.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  virt/kvm/assigned-dev.c | 36 ++++++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
> index 23a41a9..3642239 100644
> --- a/virt/kvm/assigned-dev.c
> +++ b/virt/kvm/assigned-dev.c
> @@ -105,6 +105,15 @@ static irqreturn_t kvm_assigned_dev_thread_intx(int irq, void *dev_id)
>  }
>  
>  #ifdef __KVM_HAVE_MSI
> +static irqreturn_t kvm_assigned_dev_msi(int irq, void *dev_id)
> +{
> +	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
> +	int ret = kvm_set_irq_inatomic(assigned_dev->kvm,
> +				       assigned_dev->irq_source_id,
> +				       assigned_dev->guest_irq, 1);
Why not use kvm_set_msi_inatomic() and drop kvm_set_irq_inatomic() from
previous patch? 

> +	return unlikely(ret == -EWOULDBLOCK) ? IRQ_WAKE_THREAD : IRQ_HANDLED;
> +}
> +
>  static irqreturn_t kvm_assigned_dev_thread_msi(int irq, void *dev_id)
>  {
>  	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
> @@ -117,6 +126,23 @@ static irqreturn_t kvm_assigned_dev_thread_msi(int irq, void *dev_id)
>  #endif
>  
>  #ifdef __KVM_HAVE_MSIX
> +static irqreturn_t kvm_assigned_dev_msix(int irq, void *dev_id)
> +{
> +	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
> +	int index = find_index_from_host_irq(assigned_dev, irq);
> +	u32 vector;
> +	int ret = 0;
> +
> +	if (index >= 0) {
> +		vector = assigned_dev->guest_msix_entries[index].vector;
> +		ret = kvm_set_irq_inatomic(assigned_dev->kvm,
> +					   assigned_dev->irq_source_id,
> +					   vector, 1);
> +	}
> +
> +	return unlikely(ret == -EWOULDBLOCK) ? IRQ_WAKE_THREAD : IRQ_HANDLED;
> +}
> +
>  static irqreturn_t kvm_assigned_dev_thread_msix(int irq, void *dev_id)
>  {
>  	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
> @@ -334,11 +360,6 @@ static int assigned_device_enable_host_intx(struct kvm *kvm,
>  }
>  
>  #ifdef __KVM_HAVE_MSI
> -static irqreturn_t kvm_assigned_dev_msi(int irq, void *dev_id)
> -{
> -	return IRQ_WAKE_THREAD;
> -}
> -
>  static int assigned_device_enable_host_msi(struct kvm *kvm,
>  					   struct kvm_assigned_dev_kernel *dev)
>  {
> @@ -363,11 +384,6 @@ static int assigned_device_enable_host_msi(struct kvm *kvm,
>  #endif
>  
>  #ifdef __KVM_HAVE_MSIX
> -static irqreturn_t kvm_assigned_dev_msix(int irq, void *dev_id)
> -{
> -	return IRQ_WAKE_THREAD;
> -}
> -
>  static int assigned_device_enable_host_msix(struct kvm *kvm,
>  					    struct kvm_assigned_dev_kernel *dev)
>  {
> -- 
> MST
> --
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--
			Gleb.