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=-15.3 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,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 AD125C433ED for ; Wed, 28 Apr 2021 09:56:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E9506141E for ; Wed, 28 Apr 2021 09:56:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238798AbhD1J4x (ORCPT ); Wed, 28 Apr 2021 05:56:53 -0400 Received: from mga14.intel.com ([192.55.52.115]:55726 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230032AbhD1J4v (ORCPT ); Wed, 28 Apr 2021 05:56:51 -0400 IronPort-SDR: lkpQhPGSx0IMmKw/ZN1ed+cFC4CR+3ZZ8AtRfWaBXYjalaIgIWaKG/wiOj4bRp/OahK2hApr6t WBgNLex10XEw== X-IronPort-AV: E=McAfee;i="6200,9189,9967"; a="196258062" X-IronPort-AV: E=Sophos;i="5.82,257,1613462400"; d="scan'208";a="196258062" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2021 02:56:06 -0700 IronPort-SDR: /jvroPBN/VZ3UMZDpzwauVfbEJ4mVOZswAFhEHEX1XPOpFgJu1IRQRcQk2hz5CEP7DN3NMMPi1 MUtnimI6c2Vg== X-IronPort-AV: E=Sophos;i="5.82,257,1613462400"; d="scan'208";a="423452748" Received: from lingshan-mobl5.ccr.corp.intel.com (HELO [10.254.209.93]) ([10.254.209.93]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2021 02:56:04 -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> From: "Zhu, Lingshan" Message-ID: Date: Wed, 28 Apr 2021 17:56:02 +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: <1984491f-cd5e-d4bc-b328-41e2f2e935fd@redhat.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: linux-kernel@vger.kernel.org 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. > > >>> 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, 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) >>> >> >