netdev - Re: [PATCH V4 0/6] IRQ offloading for vDPA

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Message-ID: <d3a12faa-44b5-1c1b-2047-7b39863d82a7@redhat.com>
Date:   Fri, 31 Jul 2020 11:18:40 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>, alex.williamson@...hat.com,
        mst@...hat.com, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, eli@...lanox.com, shahafs@...lanox.com,
        parav@...lanox.com
Subject: Re: [PATCH V4 0/6] IRQ offloading for vDPA


On 2020/7/28 下午12:23, Zhu Lingshan wrote:
> 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.
> changes from V3:
> (1)removed vDPA irq allocate/free helpers in vDPA core.
> (2)add a new function get_vq_irq() in struct vdpa_config_ops,
> upper layer driver can use this function to: A. query the
> irq numbner of a vq. B. detect whether a vq is enabled.
> (3)implement get_vq_irq() in ifcvf driver.
> (4)in vhost_vdpa, set_status() will setup irq offloading when
> setting DRIVER_OK, and unsetup when receive !DRIVER_OK.
> (5)minor improvements.


Ok, I think you can go ahead to post a V5. It's not bad to start with 
get_vq_irq() and we can do any changes afterwards if it can work for 
some cases.

Thanks