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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 2C1A4C433E6 for ; Fri, 29 Jan 2021 07:45:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5B7D64E08 for ; Fri, 29 Jan 2021 07:45:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232428AbhA2Hp1 (ORCPT ); Fri, 29 Jan 2021 02:45:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:42924 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232076AbhA2HpV (ORCPT ); Fri, 29 Jan 2021 02:45:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611906235; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sdvP+XB+ujK4GwLPOzeUg9idInwSrrIU7VqOTnRaTYc=; b=DC6rBaLbegs9VTM64v2AwtVedNCV0mHliFawxR/aoavX5tV/DKtnbQV/uIu/0YD0Ich6dB kXUsfeHi9eNXN+FrGubDQzJIQk+Nhu/MZL/5BnsPSFAavp7ClKGkrPNNQgHGnZ6EKc6E65 KnuhbSh92NAgvV69VKAcK8mDHkSsLeg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-38-6hE_-NqCOc6xnv-fnGRljg-1; Fri, 29 Jan 2021 02:43:52 -0500 X-MC-Unique: 6hE_-NqCOc6xnv-fnGRljg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EA3DD107ACFA; Fri, 29 Jan 2021 07:43:50 +0000 (UTC) Received: from [10.72.14.10] (ovpn-14-10.pek2.redhat.com [10.72.14.10]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3C0E371C8E; Fri, 29 Jan 2021 07:43:41 +0000 (UTC) Subject: Re: [PATCH RFC v2 02/10] vringh: add 'iotlb_lock' to synchronize iotlb accesses To: Stefano Garzarella , virtualization@lists.linux-foundation.org Cc: Xie Yongji , "Michael S. Tsirkin" , Laurent Vivier , Stefan Hajnoczi , linux-kernel@vger.kernel.org, Max Gurtovoy , kvm@vger.kernel.org References: <20210128144127.113245-1-sgarzare@redhat.com> <20210128144127.113245-3-sgarzare@redhat.com> From: Jason Wang Message-ID: <017f6e69-b2ec-aed0-5920-a389199e4cf9@redhat.com> Date: Fri, 29 Jan 2021 15:43:40 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210128144127.113245-3-sgarzare@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/1/28 下午10:41, Stefano Garzarella wrote: > Usually iotlb accesses are synchronized with a spinlock. > Let's request it as a new parameter in vringh_set_iotlb() and > hold it when we navigate the iotlb in iotlb_translate() to avoid > race conditions with any new additions/deletions of ranges from > the ioltb. Patch looks fine but I wonder if this is the best approach comparing to do locking by the caller. Thanks > > Signed-off-by: Stefano Garzarella > --- > include/linux/vringh.h | 6 +++++- > drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- > drivers/vhost/vringh.c | 9 ++++++++- > 3 files changed, 15 insertions(+), 3 deletions(-) > > diff --git a/include/linux/vringh.h b/include/linux/vringh.h > index 59bd50f99291..9c077863c8f6 100644 > --- a/include/linux/vringh.h > +++ b/include/linux/vringh.h > @@ -46,6 +46,9 @@ struct vringh { > /* IOTLB for this vring */ > struct vhost_iotlb *iotlb; > > + /* spinlock to synchronize IOTLB accesses */ > + spinlock_t *iotlb_lock; > + > /* The function to call to notify the guest about added buffers */ > void (*notify)(struct vringh *); > }; > @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) > > #if IS_REACHABLE(CONFIG_VHOST_IOTLB) > > -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); > +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, > + spinlock_t *iotlb_lock); > > int vringh_init_iotlb(struct vringh *vrh, u64 features, > unsigned int num, bool weak_barriers, > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c > index 2183a833fcf4..53238989713d 100644 > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c > @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr) > goto err_iommu; > > for (i = 0; i < dev_attr->nvqs; i++) > - vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu); > + vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu, > + &vdpasim->iommu_lock); > > ret = iova_cache_get(); > if (ret) > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > index 85d85faba058..f68122705719 100644 > --- a/drivers/vhost/vringh.c > +++ b/drivers/vhost/vringh.c > @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh *vrh, > int ret = 0; > u64 s = 0; > > + spin_lock(vrh->iotlb_lock); > + > while (len > s) { > u64 size, pa, pfn; > > @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh *vrh, > ++ret; > } > > + spin_unlock(vrh->iotlb_lock); > + > return ret; > } > > @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); > * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. > * @vrh: the vring > * @iotlb: iotlb associated with this vring > + * @iotlb_lock: spinlock to synchronize the iotlb accesses > */ > -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) > +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, > + spinlock_t *iotlb_lock) > { > vrh->iotlb = iotlb; > + vrh->iotlb_lock = iotlb_lock; > } > EXPORT_SYMBOL(vringh_set_iotlb); >