From: "Michael S. Tsirkin" <mst@redhat.com> To: Stefano Garzarella <sgarzare@redhat.com> Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, stefanha@redhat.com, Jason Wang <jasowang@redhat.com>, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC PATCH] vhost: cache avail index in vhost_enable_notify() Date: Thu, 13 Jan 2022 10:19:46 -0500 [thread overview] Message-ID: <20220113101922-mutt-send-email-mst@kernel.org> (raw) In-Reply-To: <20220113145642.205388-1-sgarzare@redhat.com> On Thu, Jan 13, 2022 at 03:56:42PM +0100, Stefano Garzarella wrote: > In vhost_enable_notify() we enable the notifications and we read > the avail index to check if new buffers have become available in > the meantime. In this case, the device would go to re-read avail > index to access the descriptor. > > As we already do in other place, we can cache the value in `avail_idx` > and compare it with `last_avail_idx` to check if there are new > buffers available. > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> I guess we can ... but what's the point? > --- > drivers/vhost/vhost.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 59edb5a1ffe2..07363dff559e 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -2543,8 +2543,9 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq) > &vq->avail->idx, r); > return false; > } > + vq->avail_idx = vhost16_to_cpu(vq, avail_idx); > > - return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx; > + return vq->avail_idx != vq->last_avail_idx; > } > EXPORT_SYMBOL_GPL(vhost_enable_notify); > > -- > 2.31.1
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com> To: Stefano Garzarella <sgarzare@redhat.com> Cc: kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, stefanha@redhat.com Subject: Re: [RFC PATCH] vhost: cache avail index in vhost_enable_notify() Date: Thu, 13 Jan 2022 10:19:46 -0500 [thread overview] Message-ID: <20220113101922-mutt-send-email-mst@kernel.org> (raw) In-Reply-To: <20220113145642.205388-1-sgarzare@redhat.com> On Thu, Jan 13, 2022 at 03:56:42PM +0100, Stefano Garzarella wrote: > In vhost_enable_notify() we enable the notifications and we read > the avail index to check if new buffers have become available in > the meantime. In this case, the device would go to re-read avail > index to access the descriptor. > > As we already do in other place, we can cache the value in `avail_idx` > and compare it with `last_avail_idx` to check if there are new > buffers available. > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> I guess we can ... but what's the point? > --- > drivers/vhost/vhost.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 59edb5a1ffe2..07363dff559e 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -2543,8 +2543,9 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq) > &vq->avail->idx, r); > return false; > } > + vq->avail_idx = vhost16_to_cpu(vq, avail_idx); > > - return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx; > + return vq->avail_idx != vq->last_avail_idx; > } > EXPORT_SYMBOL_GPL(vhost_enable_notify); > > -- > 2.31.1 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2022-01-13 15:19 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-01-13 14:56 [RFC PATCH] vhost: cache avail index in vhost_enable_notify() Stefano Garzarella 2022-01-13 14:56 ` Stefano Garzarella 2022-01-13 15:19 ` Michael S. Tsirkin [this message] 2022-01-13 15:19 ` Michael S. Tsirkin 2022-01-13 15:44 ` Stefano Garzarella 2022-01-13 15:44 ` Stefano Garzarella 2022-01-13 16:05 ` Michael S. Tsirkin 2022-01-13 16:05 ` Michael S. Tsirkin 2022-01-14 6:18 ` Jason Wang 2022-01-14 6:18 ` Jason Wang 2022-01-14 8:02 ` Stefano Garzarella 2022-01-14 8:02 ` Stefano Garzarella
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