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Mon, 31 May 2021 20:32:00 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id r11sm12553574pgl.34.2021.05.31.20.31.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 31 May 2021 20:32:00 -0700 (PDT) Subject: Re: [PATCH V2 RESEND 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 References: <20210531073316.363655-1-lingshan.zhu@intel.com> <20210531073316.363655-3-lingshan.zhu@intel.com> <5dbdc6a5-1510-9411-6b85-d947d091089c@intel.com> From: Jason Wang Message-ID: <91c64c0c-7b78-4c41-a6d7-6d9f084c7cc5@redhat.com> Date: Tue, 1 Jun 2021 11:31:56 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <5dbdc6a5-1510-9411-6b85-d947d091089c@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 在 2021/6/1 上午11:27, Zhu, Lingshan 写道: > > > On 5/31/2021 3:56 PM, Jason Wang wrote: >> >> 在 2021/5/31 下午3:33, 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 | 17 +++++++++++++++++ >>>   1 file changed, 17 insertions(+) >>> >>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c >>> b/drivers/vdpa/ifcvf/ifcvf_main.c >>> index ab0ab5cf0f6e..effb0e549135 100644 >>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c >>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c >>> @@ -413,6 +413,22 @@ 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_adapter *adapter = vdpa_to_adapter(vdpa_dev); >>> +    struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev); >>> +    struct pci_dev *pdev = adapter->pdev; >>> +    struct vdpa_notification_area area; >>> + >>> +    area.addr = vf->vring[idx].notify_pa; >>> +    area.size = PAGE_SIZE; >>> +    if (area.addr % PAGE_SIZE) >>> +        IFCVF_DBG(pdev, "vq %u doorbell address is not PAGE_SIZE >>> aligned\n", idx); >> >> >> Let's leave the decision to upper layer by: (see >> vp_vdpa_get_vq_notification) >> >> area.addr = notify_pa; >> area.size = notify_offset_multiplier; >> >> Thanks > > Hi Jason, > > notify_offset_multiplier can be zero, means vqs share the same > doorbell address, distinguished by qid. > and in vdpa.c: > >         if (vma->vm_end - vma->vm_start != notify.size) >                 return -ENOTSUPP; > > so a zero size would cause this feature failure. > mmap should work on at least a page, so if we really want "area.size = > notify_offset_multiplier;" > I think we should add some code in vdpa.c, like: > > if(!notify.size) >     notify.size = PAGE_SIZE; > > sounds good? It's the responsibility of the driver to report a correct one. So I think it's better to tweak it as: area.size = notify_offset_multiplier ?: PAGE_SIZE; Thanks > > Thanks > Zhu Lingshan >> >> >>> + >>> +    return area; >>> +} >>> + >>>   /* >>>    * IFCVF currently does't have on-chip IOMMU, so not >>>    * implemented set_map()/dma_map()/dma_unmap() >>> @@ -440,6 +456,7 @@ 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) >> >