Re: [PATCH V2 2/6] kvm: detect assigned device via irqbypass manager
From: Alex Williamson <hidden>
Date: 2020-07-17 18:08:30
Also in:
kvm, virtualization
On Thu, 16 Jul 2020 19:23:45 +0800 Zhu Lingshan [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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