Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766AbbDGPBq (ORCPT ); Tue, 7 Apr 2015 11:01:46 -0400 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:49278 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753913AbbDGPBl (ORCPT ); Tue, 7 Apr 2015 11:01:41 -0400 Date: Tue, 7 Apr 2015 17:01:31 +0200 From: Cornelia Huck To: Greg Kurz Cc: Rusty Russell , "Michael S. Tsirkin" , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v3 7/7] vhost: feature to set the vring endianness Message-ID: <20150407170131.3899d62c.cornelia.huck@de.ibm.com> In-Reply-To: <20150407121557.4213.95569.stgit@bahia.lab.toulouse-stg.fr.ibm.com> References: <20150407120929.4213.8225.stgit@bahia.lab.toulouse-stg.fr.ibm.com> <20150407121557.4213.95569.stgit@bahia.lab.toulouse-stg.fr.ibm.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz =?UTF-8?B?R2VzY2jDpGZ0c2bDvGhydW5nOg==?= Dirk Wittkopp Sitz der Gesellschaft: =?UTF-8?B?QsO2Ymxpbmdlbg==?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15040715-0009-0000-0000-000003BCDF19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2347 Lines: 78 On Tue, 07 Apr 2015 14:19:31 +0200 Greg Kurz wrote: > This patch brings cross-endian support to vhost when used to implement > legacy virtio devices. Since it is a relatively rare situation, the > feature availability is controlled by a kernel config option (not set > by default). > > The ioctls introduced by this patch are for legacy only: virtio 1.0 > devices are returned EPERM. > > Signed-off-by: Greg Kurz > --- > drivers/vhost/Kconfig | 10 ++++++++ > drivers/vhost/vhost.c | 55 ++++++++++++++++++++++++++++++++++++++++++++ > drivers/vhost/vhost.h | 17 +++++++++++++- > include/uapi/linux/vhost.h | 5 ++++ > 4 files changed, 86 insertions(+), 1 deletion(-) > +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY > +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq, > + void __user *argp) > +{ > + struct vhost_vring_state s; > + > + if (vhost_has_feature(vq, VIRTIO_F_VERSION_1)) > + return -EPERM; > + > + if (copy_from_user(&s, argp, sizeof(s))) > + return -EFAULT; > + > + vq->legacy_is_little_endian = !!s.num; > + return 0; > +} > + > +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq, > + u32 idx, > + void __user *argp) > +{ > + struct vhost_vring_state s = { > + .index = idx, > + .num = vq->legacy_is_little_endian > + }; > + > + if (vhost_has_feature(vq, VIRTIO_F_VERSION_1)) > + return -EPERM; > + > + if (copy_to_user(argp, &s, sizeof(s))) > + return -EFAULT; > + > + return 0; > +} > +#else > +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq, > + void __user *argp) > +{ > + return 0; I'm wondering whether this handler should return an error if the feature is not configured for the kernel? How can the userspace caller find out whether it has successfully prompted the kernel to handle the endianness correctly? > +} > + > +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq, > + u32 idx, > + void __user *argp) > +{ > + return 0; > +} > +#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/