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Wed, 28 Apr 2021 10:03:41 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-12-25.pek2.redhat.com [10.72.12.25]) by smtp.corp.redhat.com (Postfix) with ESMTP id C481B5D9C6; Wed, 28 Apr 2021 10:03:35 +0000 (UTC) Subject: Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf To: "Zhu, Lingshan" , mst@redhat.com Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210428082133.6766-1-lingshan.zhu@intel.com> <20210428082133.6766-3-lingshan.zhu@intel.com> <5052fced-cd9a-e453-5cb2-39cdde60a208@intel.com> <1984491f-cd5e-d4bc-b328-41e2f2e935fd@redhat.com> From: Jason Wang Message-ID: <4e0eda74-04ac-a889-471b-03fe65c65606@redhat.com> Date: Wed, 28 Apr 2021 18:03:34 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 在 2021/4/28 下午5:56, Zhu, Lingshan 写道: > > > On 4/28/2021 5:21 PM, Jason Wang wrote: >> >> 在 2021/4/28 下午4:59, Zhu, Lingshan 写道: >>> >>> >>> On 4/28/2021 4:42 PM, Jason Wang wrote: >>>> >>>> 在 2021/4/28 下午4:21, Zhu Lingshan 写道: >>>>> This commit implements doorbell mapping feature for ifcvf. >>>>> This feature maps the notify page to userspace, to eliminate >>>>> vmexit when kick a vq. >>>>> >>>>> Signed-off-by: Zhu Lingshan >>>>> --- >>>>>   drivers/vdpa/ifcvf/ifcvf_main.c | 18 ++++++++++++++++++ >>>>>   1 file changed, 18 insertions(+) >>>>> >>>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c >>>>> b/drivers/vdpa/ifcvf/ifcvf_main.c >>>>> index e48e6b74fe2e..afcb71bc0f51 100644 >>>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c >>>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c >>>>> @@ -413,6 +413,23 @@ static int ifcvf_vdpa_get_vq_irq(struct >>>>> vdpa_device *vdpa_dev, >>>>>       return vf->vring[qid].irq; >>>>>   } >>>>>   +static struct vdpa_notification_area >>>>> ifcvf_get_vq_notification(struct vdpa_device *vdpa_dev, >>>>> +                                   u16 idx) >>>>> +{ >>>>> +    struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev); >>>>> +    struct vdpa_notification_area area; >>>>> + >>>>> +    if (vf->notify_pa % PAGE_SIZE) { >>>>> +        area.addr = 0; >>>>> +        area.size = 0; >>>> >>>> >>>> We don't need this since: >>>> >>>> 1) there's a check in the vhost vDPA >>> I think you mean this code block in vdpa.c >>>         notify = ops->get_vq_notification(vdpa, index); >>>         if (notify.addr & (PAGE_SIZE - 1)) >>>                 return -EINVAL; >>> >>> This should work, however, I think the parent driver should ensure >>> it passes a PAGE_SIZE aligned address to userspace, to be robust, to >>> be reliable. >> >> >> The point is parent is unaware of whether or not there's a userspace. > when calling this, I think it targets a usersapce program, why kernel > space need it, so IMHO no harm if we check this to keep the parent > driver robust. Again, vDPA device is unaware of what driver that is bound. It could be virtio-vpda, vhost-vdpa or other in the future. It's only the vDPA bus driver know how it is actually used. >> >> >>>> 2) device is unaware of the bound driver, non page aligned doorbell >>>> doesn't necessarily meant it can be used >>> Yes, non page aligned doorbell can not be used, so there is a check. >> >> >> Typo, what I meant is "it can't be used". That is to say, we should >> let the vDPA bus driver to decide whether or not it can be used. > If it is not page aligned, there would be extra complexities for > vhost/qemu, I see it as a hardware defect, It is allowed by the virtio spec, isn't it? Thanks > why adapt to this kind of defects? > > Thanks > Zhu Lingshan >> >> Thanks >> >> >>> >>> Thanks >>> Zhu Lingshan >>>> >>>> Let's leave those polices to the driver. >>>> >>>> Thanks >>>> >>>> >>>>> +    } else { >>>>> +        area.addr = vf->notify_pa; >>>>> +        area.size = PAGE_SIZE; >>>>> +    } >>>>> + >>>>> +    return area; >>>>> +} >>>>> + >>>>>   /* >>>>>    * IFCVF currently does't have on-chip IOMMU, so not >>>>>    * implemented set_map()/dma_map()/dma_unmap() >>>>> @@ -440,6 +457,7 @@ static const struct vdpa_config_ops >>>>> ifc_vdpa_ops ={ >>>>>       .get_config    = ifcvf_vdpa_get_config, >>>>>       .set_config    = ifcvf_vdpa_set_config, >>>>>       .set_config_cb  = ifcvf_vdpa_set_config_cb, >>>>> +    .get_vq_notification = ifcvf_get_vq_notification, >>>>>   }; >>>>>     static int ifcvf_probe(struct pci_dev *pdev, const struct >>>>> pci_device_id *id) >>>> >>> >> >