From patchwork Fri Apr 24 12:27:24 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 6269771 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 2B94E9F313 for ; Fri, 24 Apr 2015 12:28:01 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 1257D20272 for ; Fri, 24 Apr 2015 12:27:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CEDEB2026F for ; Fri, 24 Apr 2015 12:27:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756847AbbDXM1h (ORCPT ); Fri, 24 Apr 2015 08:27:37 -0400 Received: from e06smtp13.uk.ibm.com ([195.75.94.109]:35301 "EHLO e06smtp13.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754833AbbDXM1d (ORCPT ); Fri, 24 Apr 2015 08:27:33 -0400 Received: from /spool/local by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Fri, 24 Apr 2015 13:27:28 +0100 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp03.portsmouth.uk.ibm.com (Postfix) with ESMTP id 040AC1B0805F; Fri, 24 Apr 2015 13:28:06 +0100 (BST) Received: from d06av09.portsmouth.uk.ibm.com (d06av09.portsmouth.uk.ibm.com [9.149.37.250]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t3OCRSxk7864698; Fri, 24 Apr 2015 12:27:28 GMT Received: from d06av09.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av09.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t3OCRRV0001197; Fri, 24 Apr 2015 06:27:28 -0600 Received: from smtp.lab.toulouse-stg.fr.ibm.com (srv01.lab.toulouse-stg.fr.ibm.com [9.101.4.1]) by d06av09.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id t3OCRRsD001190; Fri, 24 Apr 2015 06:27:27 -0600 Received: from bahia.local (sig-9-84-138-12.evts.de.ibm.com [9.84.138.12]) by smtp.lab.toulouse-stg.fr.ibm.com (Postfix) with ESMTP id 50A94220120; Fri, 24 Apr 2015 14:27:25 +0200 (CEST) Subject: [PATCH v6 7/8] vhost: cross-endian support for legacy devices From: Greg Kurz To: Rusty Russell , "Michael S. Tsirkin" Cc: Thomas Huth , kvm@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Cornelia Huck Date: Fri, 24 Apr 2015 14:27:24 +0200 Message-ID: <20150424122632.19156.88058.stgit@bahia.local> In-Reply-To: <20150424122211.19156.97626.stgit@bahia.local> References: <20150424122211.19156.97626.stgit@bahia.local> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15042412-0013-0000-0000-000003C5C45A Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 vq->is_le boolean field is added to cache the endianness to be used for ring accesses. It defaults to native endian, as expected by legacy virtio devices. When the ring gets active, we force little endian if the device is modern. When the ring is deactivated, we revert to the native endian default. If cross-endian was compiled in, a vq->user_be boolean field is added so that userspace may request a specific endianness. This field is used to override the default when activating the ring of a legacy device. It has no effect on modern devices. Signed-off-by: Greg Kurz Reviewed-by: Cornelia Huck Reviewed-by: David Gibson --- Changes since v5: - fixed description in Kconfig - fixed error description in uapi header - dropped useless semi-colon in the vhost_vq_reset_user_be() stub drivers/vhost/Kconfig | 15 ++++++++ drivers/vhost/vhost.c | 85 +++++++++++++++++++++++++++++++++++++++++++- drivers/vhost/vhost.h | 11 +++++- include/uapi/linux/vhost.h | 14 +++++++ 4 files changed, 122 insertions(+), 3 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig index 017a1e8..533eaf0 100644 --- a/drivers/vhost/Kconfig +++ b/drivers/vhost/Kconfig @@ -32,3 +32,18 @@ config VHOST ---help--- This option is selected by any driver which needs to access the core of vhost. + +config VHOST_CROSS_ENDIAN_LEGACY + bool "Cross-endian support for vhost" + default n + ---help--- + This option allows vhost to support guests with a different byte + ordering from host while using legacy virtio. + + Userspace programs can control the feature using the + VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls. + + This is only useful on a few platforms (ppc64 and arm64). Since it + adds some overhead, it is disabled by default. + + If unsure, say "N". diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2ee2826..9e8e004 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -36,6 +36,77 @@ enum { #define vhost_used_event(vq) ((__virtio16 __user *)&vq->avail->ring[vq->num]) #define vhost_avail_event(vq) ((__virtio16 __user *)&vq->used->ring[vq->num]) +#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY +static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq) +{ + vq->user_be = !virtio_legacy_is_little_endian(); +} + +static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) +{ + struct vhost_vring_state s; + + if (vq->private_data) + return -EBUSY; + + if (copy_from_user(&s, argp, sizeof(s))) + return -EFAULT; + + if (s.num != VHOST_VRING_LITTLE_ENDIAN && + s.num != VHOST_VRING_BIG_ENDIAN) + return -EINVAL; + + vq->user_be = s.num; + + return 0; +} + +static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx, + int __user *argp) +{ + struct vhost_vring_state s = { + .index = idx, + .num = vq->user_be + }; + + if (copy_to_user(argp, &s, sizeof(s))) + return -EFAULT; + + return 0; +} + +static void vhost_init_is_le(struct vhost_virtqueue *vq) +{ + /* Note for legacy virtio: user_be is initialized at reset time + * according to the host endianness. If userspace does not set an + * explicit endianness, the default behavior is native endian, as + * expected by legacy virtio. + */ + vq->is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq->user_be; +} +#else +static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq) +{ +} + +static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp) +{ + return -ENOIOCTLCMD; +} + +static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx, + int __user *argp) +{ + return -ENOIOCTLCMD; +} + +static void vhost_init_is_le(struct vhost_virtqueue *vq) +{ + if (vhost_has_feature(vq, VIRTIO_F_VERSION_1)) + vq->is_le = true; +} +#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */ + static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh, poll_table *pt) { @@ -199,6 +270,8 @@ static void vhost_vq_reset(struct vhost_dev *dev, vq->call = NULL; vq->log_ctx = NULL; vq->memory = NULL; + vq->is_le = virtio_legacy_is_little_endian(); + vhost_vq_reset_user_be(vq); } static int vhost_worker(void *data) @@ -806,6 +879,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp) } else filep = eventfp; break; + case VHOST_SET_VRING_ENDIAN: + r = vhost_set_vring_endian(vq, argp); + break; + case VHOST_GET_VRING_ENDIAN: + r = vhost_get_vring_endian(vq, idx, argp); + break; default: r = -ENOIOCTLCMD; } @@ -1044,8 +1123,12 @@ int vhost_init_used(struct vhost_virtqueue *vq) { __virtio16 last_used_idx; int r; - if (!vq->private_data) + if (!vq->private_data) { + vq->is_le = virtio_legacy_is_little_endian(); return 0; + } + + vhost_init_is_le(vq); r = vhost_update_used_flags(vq); if (r) diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index a4fa33a..ce6f6da 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -106,6 +106,14 @@ struct vhost_virtqueue { /* Log write descriptors */ void __user *log_base; struct vhost_log *log; + + /* Ring endianness. Defaults to legacy native endianness. + * Set to true when starting a modern virtio device. */ + bool is_le; +#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY + /* Ring endianness requested by userspace for cross-endian support. */ + bool user_be; +#endif }; struct vhost_dev { @@ -175,8 +183,7 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit) static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq) { - return vhost_has_feature(vq, VIRTIO_F_VERSION_1) || - virtio_legacy_is_little_endian(); + return vq->is_le; } /* Memory accessors */ diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h index bb6a5b4..ab373191 100644 --- a/include/uapi/linux/vhost.h +++ b/include/uapi/linux/vhost.h @@ -103,6 +103,20 @@ struct vhost_memory { /* Get accessor: reads index, writes value in num */ #define VHOST_GET_VRING_BASE _IOWR(VHOST_VIRTIO, 0x12, struct vhost_vring_state) +/* Set the vring byte order in num. Valid values are VHOST_VRING_LITTLE_ENDIAN + * or VHOST_VRING_BIG_ENDIAN (other values return -EINVAL). + * The byte order cannot be changed while the device is active: trying to do so + * returns -EBUSY. + * This is a legacy only API that is simply ignored when VIRTIO_F_VERSION_1 is + * set. + * Not all kernel configurations support this ioctl, but all configurations that + * support SET also support GET. + */ +#define VHOST_VRING_LITTLE_ENDIAN 0 +#define VHOST_VRING_BIG_ENDIAN 1 +#define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct vhost_vring_state) +#define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct vhost_vring_state) + /* The following ioctls use eventfd file descriptors to signal and poll * for events. */