From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0A0CC43460 for ; Thu, 29 Apr 2021 11:26:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83F906142A for ; Thu, 29 Apr 2021 11:26:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233500AbhD2L1M (ORCPT ); Thu, 29 Apr 2021 07:27:12 -0400 Received: from mga03.intel.com ([134.134.136.65]:25966 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230148AbhD2L1K (ORCPT ); Thu, 29 Apr 2021 07:27:10 -0400 IronPort-SDR: bnyy8rVzjFI5xhK0bs8y4Km/MubCcK/VuLQlst4JM8XlCwgrirRcKaIx1E9CPKK5Oy1ksEqBiw 7uVPm8Yq7cAg== X-IronPort-AV: E=McAfee;i="6200,9189,9968"; a="197029050" X-IronPort-AV: E=Sophos;i="5.82,259,1613462400"; d="scan'208";a="197029050" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Apr 2021 04:26:18 -0700 IronPort-SDR: 6rR9y8kmfinDUbQKppRZ/uP7sAONhZL9QHkj0hsR2petOMhD4RcjAcsVG9avvMqHSm/TJ53V0B 2zgSBYfu6JHQ== X-IronPort-AV: E=Sophos;i="5.82,259,1613462400"; d="scan'208";a="526904265" Received: from xli56-mobl.ccr.corp.intel.com (HELO [10.254.211.239]) ([10.254.211.239]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Apr 2021 04:26:16 -0700 Subject: Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf To: Jason Wang , 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> <4e0eda74-04ac-a889-471b-03fe65c65606@redhat.com> From: "Zhu, Lingshan" Message-ID: Date: Thu, 29 Apr 2021 19:26:14 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/28/2021 9:08 PM, Jason Wang wrote: > > 在 2021/4/28 下午6:20, Zhu, Lingshan 写道: >> >> >> On 4/28/2021 6:03 PM, Jason Wang wrote: >>> >>> 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? >> The spec does not require the doorbell to be page size aligned, >> however it still a hardware defect if non page size aligned notify >> base present, I will leave a warning message here instead of the 0 >> value. >> > > Another note is that, using PAGE_SIZE is wrong here since it varies > among archs (at most 64K on some one). For the page alignment checks, I think this is the point of using PAGE_SIZE, we want the doorbell placed at the page boundary, PAGE_SIZE depends on the arch, so I think we don't want to use hard code here. We will pass the notify_pa to upper layer anyway, just print an warning if not PAGE_SIZE aligned. However I think this may refer to vdpa_notification_area.size, YES, I think use PAGE_SIZE directly is wrong here, this size depends on the device(bar layout) than the arch, so I will add more code to tell which device is probed by the driver, then assign correct value. Thanks > > Thanks > > >> Thanks >> Zhu Lingshan >>> >>> 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) >>>>>>> >>>>>> >>>>> >>>> >>> >> >