On Thu, Jul 16, 2020 at 09:39:17AM +0800, Zhu, Lingshan
wrote:>
> On 7/15/2020 9:43 PM, Jason Wang wrote:
>
>
> On 2020/7/12 ??10:52, Zhu Lingshan wrote:
>
> Hi All,
>
> This series intends to implement IRQ offloading for
> vhost_vdpa.
>
> By the feat of irq forwarding facilities like posted
> interrupt on X86, irq bypass can? help deliver
> interrupts to vCPU directly.
>
> vDPA devices have dedicated hardware backends like VFIO
> pass-throughed devices. So it would be possible to setup
> irq offloading(irq bypass) for vDPA devices and gain
> performance improvements.
>
> In my testing, with this feature, we can save 0.1ms
> in a ping between two VFs on average.
>
>
>
> Hi Lingshan:
>
> During the virtio-networking meeting, Michael spots two possible
issues:
>
> 1) do we need an new uAPI to stop the irq offloading?
> 2) can interrupt lost during the eventfd ctx?
>
> For 1) I think we probably not, we can allocate an independent eventfd
> which does not map to MSIX. So the consumer can't match the
producer and we
> fallback to eventfd based irq.
>
> Hi Jason,
>
> I wonder why we need to stop irq offloading, but if we need to do so, maybe
a new uAPI would be more intuitive to me,
> but why and who(user? qemu?) shall initialize this process, based on what
kinda of basis to make the decision?
>
> For 2) it looks to me guest should deal with the irq synchronization
when
> mask or unmask MSIX vectors.
>
> Agreed!
Well we need to make sure during a switch each interrupt is reported
*somewhere*: either irq or eventfd - and not lost.
> Thanks,
> BR
> Zhu Lingshan
>
>
> What's your thought?
>
> Thanks
>
>
>
>
>
> Zhu Lingshan (7):
> ?? vhost: introduce vhost_call_ctx
> ?? kvm/vfio: detect assigned device via irqbypass manager
> ?? vhost_vdpa: implement IRQ offloading functions in vhost_vdpa
> ?? vDPA: implement IRQ offloading helpers in vDPA core
> ?? virtio_vdpa: init IRQ offloading function pointers to NULL.
> ?? ifcvf: replace irq_request/free with helpers in vDPA core.
> ?? irqbypass: do not start consumer or producer when failed to
connect
>
> ? arch/x86/kvm/x86.c????????????? | 10 ++++--
> ? drivers/vdpa/ifcvf/ifcvf_main.c | 11 +++---
> ? drivers/vdpa/vdpa.c???????????? | 46 +++++++++++++++++++++++++
> ? drivers/vhost/Kconfig?????????? |? 1 +
> ? drivers/vhost/vdpa.c??????????? | 75
> +++++++++++++++++++++++++++++++++++++++--
> ? drivers/vhost/vhost.c?????????? | 22 ++++++++----
> ? drivers/vhost/vhost.h?????????? |? 9 ++++-
> ? drivers/virtio/virtio_vdpa.c??? |? 2 ++
> ? include/linux/vdpa.h??????????? | 11 ++++++
> ? virt/kvm/vfio.c???????????????? |? 2 --
> ? virt/lib/irqbypass.c??????????? | 16 +++++----
> ? 11 files changed, 181 insertions(+), 24 deletions(-)
>
>
>
>
