On Tue, Jul 14, 2020 at 08:52:43AM +0800, Zhu, Lingshan wrote:

On 7/13/2020 6:52 PM, Michael S. Tsirkin wrote:

    On Mon, Jul 13, 2020 at 04:13:35PM +0800, Jason Wang wrote:

        On 2020/7/13 上午5:06, Michael S. Tsirkin wrote:

            On Sun, Jul 12, 2020 at 10:49:21PM +0800, Zhu Lingshan 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.

                Signed-off-by: Zhu Lingshan [off-list ref]

            I think it's best to leave VFIO alone. Add appropriate APIs for VDPA,
            worry about converting existing users later.



        Just to make sure I understand, did you mean:

        1) introduce another bridge for vDPA

        or

        2) only detect vDPA via bypass manager? (we can leave VFIO code as is, then
        the assigned device counter may increase/decrease twice if VFIO use irq
        bypass manager which should be no harm).

        Thanks

    2 is probably easier to justify. 1 would depend on the specific bridge
    proposed.

Thanks Michael, so we should just drop changes in vfio, just increase / decrease
the counter in irq bypass manager. right?

Thanks

I don't see any issue with that.

                ---
                  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);
                --
                1.8.3.1