Received: by 2002:a25:8b12:0:0:0:0:0 with SMTP id i18csp2945538ybl; Sun, 1 Sep 2019 03:27:38 -0700 (PDT) X-Google-Smtp-Source: APXvYqwCV6RUxIRN5/B6+5zh9CgJRA9gLvOPE01HE7tSIRG4VWCH2UebMQRY2PFHjS7yQv47nIpI X-Received: by 2002:aa7:8082:: with SMTP id v2mr19669991pff.44.1567333657961; Sun, 01 Sep 2019 03:27:37 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1567333657; cv=none; d=google.com; s=arc-20160816; b=xR2iVx2roPcs8FBVeOA+N7QFIsAS8TadQ5m2tAOKFPXj4JGXiZ97963QsyprRjNTZZ iyknwDs/gJV4iBIvUui/RoXyF0qttDIDcdAEHSbjkouAPeoXP5BOrprdQ5CerIrfwJKj /0jjW8Mn0NTOAOlJ5KkTRI07r7uoBpCL/4KlKGvUhrgFKqBwLC84xN+sRy8NVvDFESFz GqYBv9K7dBYRDDMMv8tNLKkw/d5NRy95tGC+d72zLC8RS13fmw5GsiW/yHnshvt5Y8Sl wQ0h13HXn/0NbEuNyqIFibVUNpLXLkiihXgT8x5jNvnSanxEcX97tS3qZb+CFYx+guJU KS5g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:in-reply-to:content-disposition :mime-version:references:message-id:subject:cc:to:from:date; bh=axJqbhswXeuOWGgZcXN6xzgPqVPx/M1YxoiXUe2de6s=; b=BOad54JuKUpQCjU9dk/dLPWDo6v/lK7im2YYzA9td3hUBMO9fmLM0nn3BCeor2CuK5 Jo4y9+/jiAReLvZQ3nlazf+w+0XcahWkd49p1FNuk9cvk7Xk3eDKj4PfgRw+ZdogxT1k YrcotWEWZDmPh8JYO6c03KfomK4wW/oSnJnMFpwVUYw3kAvnPFNc/ZB/cfwIPG/yjgHS cPyGjxgj03tPGP5CMs4crhZnafIphkRhF5d3XTucenuVTd7mzrP0m2Yn8aer9/OWbGPK lzPIQP3oQYGYCDLZ1P11OCbvCh/lhKh93VIhOWRFAUizu7+zkPv0qJZp+QxJdwgG/m5s SCJg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id t3si9300537pjq.95.2019.09.01.03.27.22; Sun, 01 Sep 2019 03:27:37 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728879AbfIAKSI (ORCPT + 99 others); Sun, 1 Sep 2019 06:18:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46626 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728390AbfIAKSG (ORCPT ); Sun, 1 Sep 2019 06:18:06 -0400 Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CC80DC049E23 for ; Sun, 1 Sep 2019 10:18:05 +0000 (UTC) Received: by mail-qt1-f200.google.com with SMTP id z20so7334575qtn.12 for ; Sun, 01 Sep 2019 03:18:05 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=axJqbhswXeuOWGgZcXN6xzgPqVPx/M1YxoiXUe2de6s=; b=e64sKCfzvXPDdXGD3u6XOE/TUsXIAgiXQOknoVbCwmrXUNlM697YdL8DfQzGxdM46M 1qXAyCYGkMxj3Th8c6OqFM8qgkN5xfe+R4f81NRtEstiC/fIa3xq6230t33ob3nLWHI9 K6fNTV3N9s+VopUs+KD+C2BgLl1NB3ztHSQ1O1QeF54HkdiTg6bqMlvnAPiVa/D/6yY2 Ot2CzKWhzQkcNQ81zgoUs+6xaklSP3gqaF1XPjxHytNHDsEgF+W8UaxAIZ6Hbp4JXWB3 HzTFNJfPum7sv/JeI4s+WTNTaYn8KVo0cmzmzELIWLYNUaLMRU4HoHoX0sFcdYFDDyb5 6D2Q== X-Gm-Message-State: APjAAAX53+04v38tlAJVhi6QxJ2MrI4zu0zSQOFu16wPb4tVpoQeRkma T37nJiGx9Xd71oL/p3mzNQrJUp2XIFDvUBXIlIiOojZb5UiqGoPA6Wmyhvcj2B7jFYcpt9MhWYB w49DjOpu2PJMViAWysvqdk/rN X-Received: by 2002:ac8:140e:: with SMTP id k14mr1730709qtj.43.1567333085151; Sun, 01 Sep 2019 03:18:05 -0700 (PDT) X-Received: by 2002:ac8:140e:: with SMTP id k14mr1730693qtj.43.1567333084878; Sun, 01 Sep 2019 03:18:04 -0700 (PDT) Received: from redhat.com (bzq-79-180-62-110.red.bezeqint.net. [79.180.62.110]) by smtp.gmail.com with ESMTPSA id s4sm5173520qkb.130.2019.09.01.03.18.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Sep 2019 03:18:03 -0700 (PDT) Date: Sun, 1 Sep 2019 06:17:58 -0400 From: "Michael S. Tsirkin" To: Stefano Garzarella Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Hajnoczi , "David S. Miller" , virtualization@lists.linux-foundation.org, Jason Wang , kvm@vger.kernel.org Subject: Re: [PATCH v4 1/5] vsock/virtio: limit the memory used per-socket Message-ID: <20190901061707-mutt-send-email-mst@kernel.org> References: <20190729114302-mutt-send-email-mst@kernel.org> <20190729161903.yhaj5rfcvleexkhc@steredhat> <20190729165056.r32uzj6om3o6vfvp@steredhat> <20190729143622-mutt-send-email-mst@kernel.org> <20190730093539.dcksure3vrykir3g@steredhat> <20190730163807-mutt-send-email-mst@kernel.org> <20190801104754.lb3ju5xjfmnxioii@steredhat> <20190801091106-mutt-send-email-mst@kernel.org> <20190801133616.sik5drn6ecesukbb@steredhat> <20190901025815-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190901025815-mutt-send-email-mst@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 01, 2019 at 04:26:19AM -0400, Michael S. Tsirkin wrote: > On Thu, Aug 01, 2019 at 03:36:16PM +0200, Stefano Garzarella wrote: > > On Thu, Aug 01, 2019 at 09:21:15AM -0400, Michael S. Tsirkin wrote: > > > On Thu, Aug 01, 2019 at 12:47:54PM +0200, Stefano Garzarella wrote: > > > > On Tue, Jul 30, 2019 at 04:42:25PM -0400, Michael S. Tsirkin wrote: > > > > > On Tue, Jul 30, 2019 at 11:35:39AM +0200, Stefano Garzarella wrote: > > > > > > > > (...) > > > > > > > > > > > > > > > > The problem here is the compatibility. Before this series virtio-vsock > > > > > > and vhost-vsock modules had the RX buffer size hard-coded > > > > > > (VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE = 4K). So, if we send a buffer smaller > > > > > > of 4K, there might be issues. > > > > > > > > > > Shouldn't be if they are following the spec. If not let's fix > > > > > the broken parts. > > > > > > > > > > > > > > > > > Maybe it is the time to add add 'features' to virtio-vsock device. > > > > > > > > > > > > Thanks, > > > > > > Stefano > > > > > > > > > > Why would a remote care about buffer sizes? > > > > > > > > > > Let's first see what the issues are. If they exist > > > > > we can either fix the bugs, or code the bug as a feature in spec. > > > > > > > > > > > > > The vhost_transport '.stream_enqueue' callback > > > > [virtio_transport_stream_enqueue()] calls the virtio_transport_send_pkt_info(), > > > > passing the user message. This function allocates a new packet, copying > > > > the user message, but (before this series) it limits the packet size to > > > > the VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (4K): > > > > > > > > static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > > > > struct virtio_vsock_pkt_info *info) > > > > { > > > > ... > > > > /* we can send less than pkt_len bytes */ > > > > if (pkt_len > VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE) > > > > pkt_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE; > > > > > > > > /* virtio_transport_get_credit might return less than pkt_len credit */ > > > > pkt_len = virtio_transport_get_credit(vvs, pkt_len); > > > > > > > > /* Do not send zero length OP_RW pkt */ > > > > if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW) > > > > return pkt_len; > > > > ... > > > > } > > > > > > > > then it queues the packet for the TX worker calling .send_pkt() > > > > [vhost_transport_send_pkt() in the vhost_transport case] > > > > > > > > The main function executed by the TX worker is > > > > vhost_transport_do_send_pkt() that picks up a buffer from the virtqueue > > > > and it tries to copy the packet (up to 4K) on it. If the buffer > > > > allocated from the guest will be smaller then 4K, I think here it will > > > > be discarded with an error: > > > > > > > > I'm adding more lines to explain better. > > > > > > static void > > > > vhost_transport_do_send_pkt(struct vhost_vsock *vsock, > > > > struct vhost_virtqueue *vq) > > > > { > > ... > > > > head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov), > > &out, &in, NULL, NULL); > > > > ... > > > > len = iov_length(&vq->iov[out], in); > > iov_iter_init(&iov_iter, READ, &vq->iov[out], in, len); > > > > nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter); > > if (nbytes != sizeof(pkt->hdr)) { > > virtio_transport_free_pkt(pkt); > > vq_err(vq, "Faulted on copying pkt hdr\n"); > > break; > > } > > > > > > ... > > > > nbytes = copy_to_iter(pkt->buf, pkt->len, &iov_iter); > > > > > > isn't pck len the actual length though? > > > > > > > It is the length of the packet that we are copying in the guest RX > > buffers pointed by the iov_iter. The guest allocates an iovec with 2 > > buffers, one for the header and one for the payload (4KB). > > BTW at the moment that forces another kmalloc within virtio core. Maybe > vsock needs a flag to skip allocation in this case. Worth benchmarking. > See virtqueue_use_indirect which just does total_sg > 1. > > > > > > > if (nbytes != pkt->len) { > > > > virtio_transport_free_pkt(pkt); > > > > vq_err(vq, "Faulted on copying pkt buf\n"); > > > > break; > > > > } > > > > ... > > > > } > > > > > > > > > > > > This series changes this behavior since now we will split the packet in > > > > vhost_transport_do_send_pkt() depending on the buffer found in the > > > > virtqueue. > > > > > > > > We didn't change the buffer size in this series, so we still backward > > > > compatible, but if we will use buffers smaller than 4K, we should > > > > encounter the error described above. > > So that's an implementation bug then? It made an assumption > of a 4K sized buffer? Or even PAGE_SIZE sized buffer? Assuming we miss nothing and buffers < 4K are broken, I think we need to add this to the spec, possibly with a feature bit to relax the requirement that all buffers are at least 4k in size. > > > > > > > > > How do you suggest we proceed if we want to change the buffer size? > > > > Maybe adding a feature to "support any buffer size"? > > > > > > > > Thanks, > > > > Stefano > > > > > > > > > > --