From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932100AbbJ0Kae (ORCPT ); Tue, 27 Oct 2015 06:30:34 -0400 Received: from e06smtp16.uk.ibm.com ([195.75.94.112]:38128 "EHLO e06smtp16.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754224AbbJ0Ka2 (ORCPT ); Tue, 27 Oct 2015 06:30:28 -0400 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, 27 Oct 2015 11:30:18 +0100 From: Greg Kurz To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH] vhost: fix performance on LE hosts Message-ID: <20151027113018.3b40bd78@bahia.local> In-Reply-To: <1445938640-32673-1-git-send-email-mst@redhat.com> References: <1445938640-32673-1-git-send-email-mst@redhat.com> Organization: IBM X-Mailer: Claws Mail 3.12.0 (GTK+ 2.24.28; 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: 15102710-0025-0000-0000-000007896801 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 Oct 2015 11:37:39 +0200 "Michael S. Tsirkin" wrote: > commit 2751c9882b947292fcfb084c4f604e01724af804 ("vhost: cross-endian > support for legacy devices") introduced a minor regression: even with > cross-endian disabled, and even on LE host, vhost_is_little_endian is > checking is_le flag so there's always a branch. > > To fix, simply check virtio_legacy_is_little_endian first. > > Cc: Greg Kurz > Signed-off-by: Michael S. Tsirkin Oops my bad for this oversight... Reviewed-by: Greg Kurz > --- > drivers/vhost/vhost.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index 4772862..d3f7674 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -183,10 +183,17 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit) > return vq->acked_features & (1ULL << bit); > } > > +#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY > static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq) > { > return vq->is_le; > } > +#else > +static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq) > +{ > + return virtio_legacy_is_little_endian() || vq->is_le; > +} > +#endif > > /* Memory accessors */ > static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)