On 2020/7/18 上午2:08, Alex Williamson wrote:

On Thu, 16 Jul 2020 19:23:45 +0800
Zhu Lingshan [off-list ref] wrote:

quoted

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.

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.

Signed-off-by: Zhu Lingshan <redacted>
Suggested-by: Jason Wang <jasowang@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,

Why isn't there a matching end-assignment in the del_producer path?  It
seems this only goes one-way, what happens when a device is
hot-unplugged from the VM or the device interrupt configuration changes.
This will still break vfio if it's not guaranteed to be symmetric.
Thanks,

Alex

Yes, we need add logic in the del_producer path.

Thanks