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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 C82B7C04AB4 for ; Tue, 14 May 2019 14:47:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96E872084E for ; Tue, 14 May 2019 14:47:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726098AbfENOrn (ORCPT ); Tue, 14 May 2019 10:47:43 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50384 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725901AbfENOrm (ORCPT ); Tue, 14 May 2019 10:47:42 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x4EEkoLN179804 for ; Tue, 14 May 2019 10:47:41 -0400 Received: from e11.ny.us.ibm.com (e11.ny.us.ibm.com [129.33.205.201]) by mx0b-001b2d01.pphosted.com with ESMTP id 2sfyqw818a-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 14 May 2019 10:47:41 -0400 Received: from localhost by e11.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 14 May 2019 15:47:37 +0100 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp22034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x4EElYmh11927646 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 May 2019 14:47:34 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 86A0B28060; Tue, 14 May 2019 14:47:34 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3856828058; Tue, 14 May 2019 14:47:34 +0000 (GMT) Received: from [9.60.75.213] (unknown [9.60.75.213]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 14 May 2019 14:47:34 +0000 (GMT) Reply-To: jjherne@linux.ibm.com Subject: Re: [PATCH 06/10] s390/cio: add basic protected virtualization support To: Cornelia Huck , Halil Pasic Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, Martin Schwidefsky , Sebastian Ott , virtualization@lists.linux-foundation.org, "Michael S. Tsirkin" , Christoph Hellwig , Thomas Huth , Christian Borntraeger , Viktor Mihajlovski , Vasily Gorbik , Janosch Frank , Claudio Imbrenda , Farhan Ali , Eric Farman References: <20190426183245.37939-1-pasic@linux.ibm.com> <20190426183245.37939-7-pasic@linux.ibm.com> <20190513114136.783c851c.cohuck@redhat.com> From: "Jason J. Herne" Organization: IBM Date: Tue, 14 May 2019 10:47:34 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190513114136.783c851c.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19051414-2213-0000-0000-0000038D9A3A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011096; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000285; SDB=6.01203230; UDB=6.00631560; IPR=6.00984152; MB=3.00026883; MTD=3.00000008; XFM=3.00000015; UTC=2019-05-14 14:47:39 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19051414-2214-0000-0000-00005E6E8108 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-05-14_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905140105 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 5/13/19 5:41 AM, Cornelia Huck wrote: > On Fri, 26 Apr 2019 20:32:41 +0200 > Halil Pasic wrote: > >> As virtio-ccw devices are channel devices, we need to use the dma area >> for any communication with the hypervisor. >> >> This patch addresses the most basic stuff (mostly what is required for >> virtio-ccw), and does take care of QDIO or any devices. > > "does not take care of QDIO", surely? (Also, what does "any devices" > mean? Do you mean "every arbitrary device", perhaps?) > >> >> An interesting side effect is that virtio structures are now going to >> get allocated in 31 bit addressable storage. > > Hm... > >> >> Signed-off-by: Halil Pasic >> --- >> arch/s390/include/asm/ccwdev.h | 4 +++ >> drivers/s390/cio/ccwreq.c | 8 ++--- >> drivers/s390/cio/device.c | 65 +++++++++++++++++++++++++++++++++------- >> drivers/s390/cio/device_fsm.c | 40 ++++++++++++------------- >> drivers/s390/cio/device_id.c | 18 +++++------ >> drivers/s390/cio/device_ops.c | 21 +++++++++++-- >> drivers/s390/cio/device_pgid.c | 20 ++++++------- >> drivers/s390/cio/device_status.c | 24 +++++++-------- >> drivers/s390/cio/io_sch.h | 21 +++++++++---- >> drivers/s390/virtio/virtio_ccw.c | 10 ------- >> 10 files changed, 148 insertions(+), 83 deletions(-) > > (...) > >> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c >> index 6d989c360f38..bb7a92316fc8 100644 >> --- a/drivers/s390/virtio/virtio_ccw.c >> +++ b/drivers/s390/virtio/virtio_ccw.c >> @@ -66,7 +66,6 @@ struct virtio_ccw_device { >> bool device_lost; >> unsigned int config_ready; >> void *airq_info; >> - u64 dma_mask; >> }; >> >> struct vq_info_block_legacy { >> @@ -1255,16 +1254,7 @@ static int virtio_ccw_online(struct ccw_device *cdev) >> ret = -ENOMEM; >> goto out_free; >> } >> - >> vcdev->vdev.dev.parent = &cdev->dev; >> - cdev->dev.dma_mask = &vcdev->dma_mask; >> - /* we are fine with common virtio infrastructure using 64 bit DMA */ >> - ret = dma_set_mask_and_coherent(&cdev->dev, DMA_BIT_MASK(64)); >> - if (ret) { >> - dev_warn(&cdev->dev, "Failed to enable 64-bit DMA.\n"); >> - goto out_free; >> - } > > This means that vring structures now need to fit into 31 bits as well, > I think? Is there any way to reserve the 31 bit restriction for channel > subsystem structures and keep vring in the full 64 bit range? (Or am I > fundamentally misunderstanding something?) > I hope I've understood everything... I'm new to virtio. But from what I'm understanding, the vring structure (a.k.a. the VirtQueue) needs to be accessed and modified by both host and guest. Therefore the page(s) holding that data need to be marked shared if using protected virtualization. This patch set makes use of DMA pages by way of swiotlb (always below 32-bit line right?) for shared memory. Therefore, a side effect is that all shared memory, including VirtQueue data will be in the DMA zone and in 32-bit memory. I don't see any restrictions on sharing pages above the 32-bit line. So it seems possible. I'm not sure how much more work it would be. I wonder if Halil has considered this? Are we worried that virtio data structures are going to be a burden on the 31-bit address space? -- -- Jason J. Herne (jjherne@linux.ibm.com)