Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753318AbbDGMTp (ORCPT ); Tue, 7 Apr 2015 08:19:45 -0400 Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:54441 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753119AbbDGMTk (ORCPT ); Tue, 7 Apr 2015 08:19:40 -0400 Subject: [PATCH v3 7/7] vhost: feature to set the vring endianness From: Greg Kurz To: Rusty Russell , "Michael S. Tsirkin" Cc: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Date: Tue, 07 Apr 2015 14:19:31 +0200 Message-ID: <20150407121557.4213.95569.stgit@bahia.lab.toulouse-stg.fr.ibm.com> In-Reply-To: <20150407120929.4213.8225.stgit@bahia.lab.toulouse-stg.fr.ibm.com> References: <20150407120929.4213.8225.stgit@bahia.lab.toulouse-stg.fr.ibm.com> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15040712-0041-0000-0000-000003F9A9DF Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5823 Lines: 186 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(-) Changes since v2: - fixed typos in Kconfig description - renamed vq->legacy_big_endian to vq->legacy_is_little_endian - vq->legacy_is_little_endian reset to default in vhost_vq_reset() - dropped VHOST_F_SET_ENDIAN_LEGACY feature - dropped struct vhost_vring_endian from the user API (re-use struct vhost_vring_state instead) - added VHOST_GET_VRING_ENDIAN_LEGACY ioctl - introduced more helpers and stubs to avoid polluting the code with ifdefs diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig index 017a1e8..0aec88c 100644 --- a/drivers/vhost/Kconfig +++ b/drivers/vhost/Kconfig @@ -32,3 +32,13 @@ config VHOST ---help--- This option is selected by any driver which needs to access the core of vhost. + +config VHOST_SET_ENDIAN_LEGACY + bool "Cross-endian support for host kernel accelerator" + default n + ---help--- + This option allows vhost to support guests with a different byte + ordering from host. It is disabled by default since it adds overhead + and it is only needed by a few platforms (powerpc and arm). + + If unsure, say "N". diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2ee2826..3529a3c 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, vq->call = NULL; vq->log_ctx = NULL; vq->memory = NULL; + vq->legacy_is_little_endian = virtio_legacy_is_little_endian(); } static int vhost_worker(void *data) @@ -630,6 +631,54 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) return 0; } +#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; +} + +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq, + u32 idx, + void __user *argp) +{ + return 0; +} +#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */ + long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp) { struct file *eventfp, *filep = NULL; @@ -806,6 +855,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp) } else filep = eventfp; break; + case VHOST_SET_VRING_ENDIAN_LEGACY: + r = vhost_set_vring_endian_legacy(vq, argp); + break; + case VHOST_GET_VRING_ENDIAN_LEGACY: + r = vhost_get_vring_endian_legacy(vq, idx, argp); + break; default: r = -ENOIOCTLCMD; } diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index 4e9a186..981ba06 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -106,6 +106,9 @@ struct vhost_virtqueue { /* Log write descriptors */ void __user *log_base; struct vhost_log *log; + + /* We need to know the device endianness with legacy virtio. */ + bool legacy_is_little_endian; }; struct vhost_dev { @@ -173,11 +176,23 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit) return vq->acked_features & (1ULL << bit); } +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY +static inline bool vhost_legacy_is_little_endian(struct vhost_virtqueue *vq) +{ + return vq->legacy_is_little_endian; +} +#else +static inline bool vhost_legacy_is_little_endian(struct vhost_virtqueue *vq) +{ + return virtio_legacy_is_little_endian(); +} +#endif + static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq) { if (vhost_has_feature(vq, VIRTIO_F_VERSION_1)) return true; - return virtio_legacy_is_little_endian(); + return vhost_legacy_is_little_endian(vq); } /* Memory accessors */ diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h index bb6a5b4..1b01a72 100644 --- a/include/uapi/linux/vhost.h +++ b/include/uapi/linux/vhost.h @@ -103,6 +103,11 @@ 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 endianness for the ring (legacy virtio only) */ +/* num is 0 for big endian, other values mean little endian */ +#define VHOST_SET_VRING_ENDIAN_LEGACY _IOW(VHOST_VIRTIO, 0x13, struct vhost_vring_state) +#define VHOST_GET_VRING_ENDIAN_LEGACY _IOW(VHOST_VIRTIO, 0x14, struct vhost_vring_state) + /* The following ioctls use eventfd file descriptors to signal and poll * for events. */ -- 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/