From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934810AbcALKbQ (ORCPT ); Tue, 12 Jan 2016 05:31:16 -0500 Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:39946 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752710AbcALKbJ (ORCPT ); Tue, 12 Jan 2016 05:31:09 -0500 X-IBM-Helo: d06dlp02.portsmouth.uk.ibm.com X-IBM-MailFrom: gkurz@linux.vnet.ibm.com X-IBM-RcptTo: kvm@vger.kernel.org;linux-kernel@vger.kernel.org;netdev@vger.kernel.org Date: Tue, 12 Jan 2016 11:31:00 +0100 From: Greg Kurz To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH] vhost: move is_le setup to the backend Message-ID: <20160112113100.60e6b872@bahia.huguette.org> In-Reply-To: <20160112115639-mutt-send-email-mst@redhat.com> References: <20160111143509.9601.15143.stgit@bahia.huguette.org> <20160112115639-mutt-send-email-mst@redhat.com> Organization: IBM X-Mailer: Claws Mail 3.13.1 (GTK+ 2.24.29; x86_64-redhat-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: 16011210-0041-0000-0000-00000722E25D Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Jan 2016 12:01:32 +0200 "Michael S. Tsirkin" wrote: > On Mon, Jan 11, 2016 at 03:39:38PM +0100, Greg Kurz wrote: > > The vq->is_le field is used to fix endianness when accessing the vring via > > the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases: > > > > 1) host is big endian and device is modern virtio > > > > 2) host has cross-endian support and device is legacy virtio with a different > > endianness than the host > > > > Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the > > VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le > > is only needed when the backend is active, it was decided to set it at > > backend start. > > > > This is currently done in vhost_init_used()->vhost_init_is_le() but it > > obfuscates the core vhost code. This patch moves the is_le setup to a > > dedicated function that is called from the backend code. > > > > Note vhost_net is the only backend that can pass vq->private_data == NULL to > > vhost_init_used(), hence the "if (sock)" branch. > > > > No behaviour change. > > > > Reviewed-by: Cornelia Huck > > Signed-off-by: Greg Kurz > > --- > > > > Hi Michael, > > > > This is a cleanup patch I had posted last year: > > > > http://patchwork.ozlabs.org/patch/538277/ > > > > I am just reposting with Cornelia's R-b. > > > > Cheers. > > > > -- > > Greg > > > > drivers/vhost/net.c | 6 ++++++ > > drivers/vhost/scsi.c | 3 +++ > > drivers/vhost/test.c | 2 ++ > > drivers/vhost/vhost.c | 12 +++++++----- > > drivers/vhost/vhost.h | 1 + > > 5 files changed, 19 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > index 9eda69e40678..d6319cb2664c 100644 > > --- a/drivers/vhost/net.c > > +++ b/drivers/vhost/net.c > > @@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) > > > > vhost_net_disable_vq(n, vq); > > vq->private_data = sock; > > + > > + if (sock) > > + vhost_set_is_le(vq); > > + else > > + vq->is_le = virtio_legacy_is_little_endian(); > > + > > r = vhost_init_used(vq); > > if (r) > > goto err_used; > > This part is kind of ugly. I think it's cleaner is the generic code. > How about we teach vhost_set_is_le to test vq->private_data and DTRT? > You're right. I'll try that. > > diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c > > index 29cfc57d496e..1f4f405ebba8 100644 > > --- a/drivers/vhost/scsi.c > > +++ b/drivers/vhost/scsi.c > > @@ -1274,6 +1274,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, > > vq = &vs->vqs[i].vq; > > mutex_lock(&vq->mutex); > > vq->private_data = vs_tpg; > > + > > + vhost_set_is_le(vq); > > + > > vhost_init_used(vq); > > mutex_unlock(&vq->mutex); > > } > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > > index f2882ac98726..b1c7df502211 100644 > > --- a/drivers/vhost/test.c > > +++ b/drivers/vhost/test.c > > @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test) > > oldpriv = vq->private_data; > > vq->private_data = priv; > > > > + vhost_set_is_le(vq); > > + > > r = vhost_init_used(&n->vqs[index]); > > > > mutex_unlock(&vq->mutex); > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index ad2146a9ab2d..e688eb801d43 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue *vq) > > } > > #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */ > > > > +void vhost_set_is_le(struct vhost_virtqueue *vq) > > +{ > > + vhost_init_is_le(vq); > > +} > > +EXPORT_SYMBOL_GPL(vhost_set_is_le); > > + > > static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh, > > poll_table *pt) > > { > > Why do we need this wrapper? Why not just export vhost_init_is_le? This is a tentative workaround to: WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable #35: FILE: drivers/vhost/vhost.c:116: +EXPORT_SYMBOL_GPL(vhost_init_is_le); Other possibility is to put the EXPORT_SYMBOL_GPL statement in both conditional compilation blocks. Maybe better ? > Or rename vhost_init_is_le->vhost_set_is_le if you prefer. > > > @@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq) > > { > > __virtio16 last_used_idx; > > int r; > > - if (!vq->private_data) { > > - vq->is_le = virtio_legacy_is_little_endian(); > > + if (!vq->private_data) > > 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 d3f767448a72..af5d33797937 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *); > > > > int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, > > unsigned int log_num, u64 len); > > +void vhost_set_is_le(struct vhost_virtqueue *vq); > > > > #define vq_err(vq, fmt, ...) do { \ > > pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \ >