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=-17.6 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=ham 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 E3A8CC433DB for ; Mon, 1 Feb 2021 05:49:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B829160C41 for ; Mon, 1 Feb 2021 05:49:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231618AbhBAFs7 (ORCPT ); Mon, 1 Feb 2021 00:48:59 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:23457 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231658AbhBAFpN (ORCPT ); Mon, 1 Feb 2021 00:45:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612158219; 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=5ZTIT6r9DAQKDIN9nnIQ8ksj8MiamUBCd7gKXxENqMM=; b=XCzlEu3hK7GvM6DDgPe8vljYPL5CEpzkg/2fqgBUbg/ZZ3nxPXRP1sUFvg74imqARFv9qN qDIKSHTvm7QY39Y5ESGqgcBNkvjgI9bbE2wuBHAoExoZfGNKBJLnnkCTCYr/OaSMSbfLCH 0mx/HfiWJohroh3ccGssby0kEg3pAKo= 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-452-Ovnzy_d2OluYL-XINZbruw-1; Mon, 01 Feb 2021 00:43:35 -0500 X-MC-Unique: Ovnzy_d2OluYL-XINZbruw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 13FBE18C89DE; Mon, 1 Feb 2021 05:43:34 +0000 (UTC) Received: from [10.72.13.120] (ovpn-13-120.pek2.redhat.com [10.72.13.120]) by smtp.corp.redhat.com (Postfix) with ESMTP id CC16227C42; Mon, 1 Feb 2021 05:43:24 +0000 (UTC) Subject: Re: [PATCH RFC v2 04/10] vringh: implement vringh_kiov_advance() 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> <20210128144127.113245-5-sgarzare@redhat.com> From: Jason Wang Message-ID: <78247eb0-8e6e-f2fa-a693-1b0f14db61dd@redhat.com> Date: Mon, 1 Feb 2021 13:43:23 +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: <20210128144127.113245-5-sgarzare@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/1/28 下午10:41, Stefano Garzarella wrote: > In some cases, it may be useful to provide a way to skip a number > of bytes in a vringh_kiov. > > Let's implement vringh_kiov_advance() for this purpose, reusing the > code from vringh_iov_xfer(). > We replace that code calling the new vringh_kiov_advance(). Acked-by: Jason Wang In the long run we need to switch to use iov iterator library instead. Thanks > > Signed-off-by: Stefano Garzarella > --- > include/linux/vringh.h | 2 ++ > drivers/vhost/vringh.c | 41 +++++++++++++++++++++++++++++------------ > 2 files changed, 31 insertions(+), 12 deletions(-) > > diff --git a/include/linux/vringh.h b/include/linux/vringh.h > index 9c077863c8f6..755211ebd195 100644 > --- a/include/linux/vringh.h > +++ b/include/linux/vringh.h > @@ -199,6 +199,8 @@ static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov) > kiov->iov = NULL; > } > > +void vringh_kiov_advance(struct vringh_kiov *kiov, size_t len); > + > int vringh_getdesc_kern(struct vringh *vrh, > struct vringh_kiov *riov, > struct vringh_kiov *wiov, > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > index bee63d68201a..4d800e4f31ca 100644 > --- a/drivers/vhost/vringh.c > +++ b/drivers/vhost/vringh.c > @@ -75,6 +75,34 @@ static inline int __vringh_get_head(const struct vringh *vrh, > return head; > } > > +/** > + * vringh_kiov_advance - skip bytes from vring_kiov > + * @iov: an iov passed to vringh_getdesc_*() (updated as we consume) > + * @len: the maximum length to advance > + */ > +void vringh_kiov_advance(struct vringh_kiov *iov, size_t len) > +{ > + while (len && iov->i < iov->used) { > + size_t partlen = min(iov->iov[iov->i].iov_len, len); > + > + iov->consumed += partlen; > + iov->iov[iov->i].iov_len -= partlen; > + iov->iov[iov->i].iov_base += partlen; > + > + if (!iov->iov[iov->i].iov_len) { > + /* Fix up old iov element then increment. */ > + iov->iov[iov->i].iov_len = iov->consumed; > + iov->iov[iov->i].iov_base -= iov->consumed; > + > + iov->consumed = 0; > + iov->i++; > + } > + > + len -= partlen; > + } > +} > +EXPORT_SYMBOL(vringh_kiov_advance); > + > /* Copy some bytes to/from the iovec. Returns num copied. */ > static inline ssize_t vringh_iov_xfer(struct vringh *vrh, > struct vringh_kiov *iov, > @@ -95,19 +123,8 @@ static inline ssize_t vringh_iov_xfer(struct vringh *vrh, > done += partlen; > len -= partlen; > ptr += partlen; > - iov->consumed += partlen; > - iov->iov[iov->i].iov_len -= partlen; > - iov->iov[iov->i].iov_base += partlen; > > - if (!iov->iov[iov->i].iov_len) { > - /* Fix up old iov element then increment. */ > - iov->iov[iov->i].iov_len = iov->consumed; > - iov->iov[iov->i].iov_base -= iov->consumed; > - > - > - iov->consumed = 0; > - iov->i++; > - } > + vringh_kiov_advance(iov, partlen); > } > return done; > }