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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6EC59CCA48C for ; Tue, 26 Jul 2022 08:08:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238275AbiGZIID (ORCPT ); Tue, 26 Jul 2022 04:08:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238233AbiGZIH7 (ORCPT ); Tue, 26 Jul 2022 04:07:59 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 102E1DF22 for ; Tue, 26 Jul 2022 01:07:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1658822877; 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=v2FS+wcLS276CjyoJxXnom+ZC/VQJoGiBzM4C9YEjwQ=; b=P6XvNV0OggGFFfkSr7IsoCZDABR5vDodtvb2vc3uA+//YJ1kWrpyploq3ijuUu6ajZMgh2 zoZJ+00tPwe0oJO0XhEy0w4iKDHAQmCWpAcaHTo2kGci+sPut7ymvubHLED3Z1f2ai9p0k 4jhxA7HQO0TgWAajy5DY4O46lglRT2s= Received: from mail-pl1-f197.google.com (mail-pl1-f197.google.com [209.85.214.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-19-YtFEC1-TOaO-oR0oxXCfOA-1; Tue, 26 Jul 2022 04:07:53 -0400 X-MC-Unique: YtFEC1-TOaO-oR0oxXCfOA-1 Received: by mail-pl1-f197.google.com with SMTP id s6-20020a170902a50600b0016d2e77252eso7999175plq.18 for ; Tue, 26 Jul 2022 01:07:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=v2FS+wcLS276CjyoJxXnom+ZC/VQJoGiBzM4C9YEjwQ=; b=LKUv2m2T3gMRJQwP0oWkC18ZJqxGEHwQ5wlGyjvhnGURX58HjOKn8g/AsG4+OnQ4z4 GnOpl4NtbqZwQueMtlefHc9FCcCskro4JsRR0d0x0YTSVGPzlm4sZU4IiUwcac7zcgws pxHyq/w+RYcNfbUZwwDRLxS7dRX8uTb5g1Xu9m8F87DIAF8hjy2/CcM0iUHaGmQBGBpg 4c5/du39jRaSrjLYxh0jUNk35ii6wy6/D0sbpraHBF68iXwwtJAoVdOPE4Tl1AI3R7Oe ObKj/veoh88SlrZ1xoQHc8OAtWE6ht6mgLRLToqftgMJkD606l2xqYfAZhM2QbtQDPEU bcoA== X-Gm-Message-State: AJIora+ZU+QhQvW4YMlLEUHFbNAz+1+0g82ImUdAWGhY+nhsL6tuXd5z 4a0Pn1JMNiD+kUOctp5h8aVlWEQY9EzQYHf5kDycKUdFkBjEasZ3bfPbHpzCLxLxe+R8bioqGSj y+IbHt6XOT0Obj7CDPJwH7QkW X-Received: by 2002:a17:90b:3ece:b0:1f0:6b2e:6fbf with SMTP id rm14-20020a17090b3ece00b001f06b2e6fbfmr35013949pjb.203.1658822872184; Tue, 26 Jul 2022 01:07:52 -0700 (PDT) X-Google-Smtp-Source: AGRyM1t6pDFB5xcS97km93rf91OBUoaDmySnwXucaOEG95lnhcHdHOmDqsphKxM28DLJ13n4R8FnIg== X-Received: by 2002:a17:90b:3ece:b0:1f0:6b2e:6fbf with SMTP id rm14-20020a17090b3ece00b001f06b2e6fbfmr35013922pjb.203.1658822871777; Tue, 26 Jul 2022 01:07:51 -0700 (PDT) Received: from [10.72.12.201] ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id o9-20020a62cd09000000b0052abfc4b4a4sm11290893pfg.12.2022.07.26.01.07.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Jul 2022 01:07:51 -0700 (PDT) Message-ID: <9d4c24de-f2cc-16a0-818a-16695946f3a3@redhat.com> Date: Tue, 26 Jul 2022 16:07:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [RFC 4/5] virtio: get desc id in order Content-Language: en-US To: Guo Zhi , eperezma@redhat.com, sgarzare@redhat.com, mst@redhat.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org References: <20220721084341.24183-1-qtxuning1999@sjtu.edu.cn> <20220721084341.24183-5-qtxuning1999@sjtu.edu.cn> From: Jason Wang In-Reply-To: <20220721084341.24183-5-qtxuning1999@sjtu.edu.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/7/21 16:43, Guo Zhi 写道: > If in order feature negotiated, we can skip the used ring to get > buffer's desc id sequentially. Let's rename the patch to something like "in order support for virtio_ring" > > Signed-off-by: Guo Zhi > --- > drivers/virtio/virtio_ring.c | 37 ++++++++++++++++++++++++++++-------- > 1 file changed, 29 insertions(+), 8 deletions(-) I don't see packed support in this patch, we need to implement that. > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index a5ec724c0..4d57a4edc 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -144,6 +144,9 @@ struct vring_virtqueue { > /* DMA address and size information */ > dma_addr_t queue_dma_addr; > size_t queue_size_in_bytes; > + > + /* In order feature batch begin here */ > + u16 next_batch_desc_begin; > } split; > > /* Available for packed ring */ > @@ -700,8 +703,10 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > } > > vring_unmap_one_split(vq, i); > - vq->split.desc_extra[i].next = vq->free_head; > - vq->free_head = head; > + if (!virtio_has_feature(vq->vq.vdev, VIRTIO_F_IN_ORDER)) { > + vq->split.desc_extra[i].next = vq->free_head; > + vq->free_head = head; > + } Let's add a comment to explain why we don't need anything if in order is neogitated. > > /* Plus final descriptor */ > vq->vq.num_free++; > @@ -743,7 +748,8 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq, > { > struct vring_virtqueue *vq = to_vvq(_vq); > void *ret; > - unsigned int i; > + __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT); > + unsigned int i, j; > u16 last_used; > > START_USE(vq); > @@ -762,11 +768,24 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq, > /* Only get used array entries after they have been exposed by host. */ > virtio_rmb(vq->weak_barriers); > > - last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); > - i = virtio32_to_cpu(_vq->vdev, > - vq->split.vring.used->ring[last_used].id); > - *len = virtio32_to_cpu(_vq->vdev, > - vq->split.vring.used->ring[last_used].len); > + if (virtio_has_feature(_vq->vdev, VIRTIO_F_IN_ORDER)) { > + /* Skip used ring and get used desc in order*/ > + i = vq->split.next_batch_desc_begin; > + j = i; > + while (vq->split.vring.desc[j].flags & nextflag) Let's don't depend on the descriptor ring which is under the control of the malicious hypervisor. Let's use desc_extra that is not visible by the hypervisor. More can be seen in this commit: 72b5e8958738 ("virtio-ring: store DMA metadata in desc_extra for split virtqueue") > + j = (j + 1) % vq->split.vring.num; > + /* move to next */ > + j = (j + 1) % vq->split.vring.num; > + vq->split.next_batch_desc_begin = j; I'm not sure I get the logic here, basically I think we should check buffer instead of descriptor here. So if vring.used->ring[last_used].id != last_used, we know all [last_used, vring.used->ring[last_used].id] have been used in a batch? > + > + /* TODO: len of buffer */ So spec said: " The skipped buffers (for which no used ring entry was written) are assumed to have been used (read or written) by the device completely. " Thanks > + } else { > + last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); > + i = virtio32_to_cpu(_vq->vdev, > + vq->split.vring.used->ring[last_used].id); > + *len = virtio32_to_cpu(_vq->vdev, > + vq->split.vring.used->ring[last_used].len); > + } > > if (unlikely(i >= vq->split.vring.num)) { > BAD_RING(vq, "id %u out of range\n", i); > @@ -2234,6 +2253,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > vq->split.avail_flags_shadow = 0; > vq->split.avail_idx_shadow = 0; > > + vq->split.next_batch_desc_begin = 0; > + > /* No callback? Tell other side not to bother us. */ > if (!callback) { > vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;