From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Stabellini Subject: Re: [PATCH v3 2/6] libxl: do not add a vkb backend to hvm guests Date: Tue, 30 Jun 2015 12:21:19 +0100 Message-ID: References: <1433930994-32527-2-git-send-email-stefano.stabellini@eu.citrix.com> <20150616145749.GC1813@zion.uk.xensource.com> <1435249141.32500.111.camel@citrix.com> <1435654263.21469.19.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1435654263.21469.19.camel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: Ian.Jackson@eu.citrix.com, xen-devel@lists.xensource.com, Wei Liu , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On Tue, 30 Jun 2015, Ian Campbell wrote: > On Mon, 2015-06-29 at 18:59 +0100, Stefano Stabellini wrote: > > On Thu, 25 Jun 2015, Ian Campbell wrote: > > > On Tue, 2015-06-16 at 16:39 +0100, Stefano Stabellini wrote: > > > > On Tue, 16 Jun 2015, Wei Liu wrote: > > > > > On Wed, Jun 10, 2015 at 11:09:50AM +0100, Stefano Stabellini wrote: > > > > > > When QEMU restricts its xenstore connection, it cannot provide PV > > > > > > backends. A separate QEMU instance is required to provide PV backends in > > > > > > userspace, such as qdisk. With two separate instances, it is not > > > > > > possible to take advantage of vkb for mouse and keyboard, as the QEMU > > > > > > that emulates the graphic card (the device model), would be separate > > > > > > from the QEMU running the vkb backend (PV QEMU). > > > > > > > > > > > > > > > > The question is that how would this affect the non-split setup. > > > > > > > > vkb is useful because emulating usb forces QEMU to wake up more often. > > > > However there is no way around it. > > > > > > Does pvfb+vkb continue to work due to code somewhere else? > > > > Yes, it continues to work as usual for PV guests. > > > > > > > Do we think anyone will actually be using emulated VGA + PV input > > > devices? > > > > VGA + PV input only works with Linux and is only useful for power > > efficiency, because if you disable usb emulation in QEMU, then QEMU > > would be able to wake up less often. Given that usb emulation is still > > on by default, I don't think that this change will have a big impact. > > My question was whether we thought anyone would be using this > non-default configuration, not what the impact on the default is. > > You gave a good reason why people might be using this facility, do you > think anyone is actually using it? I don't know of anybody using it. I don't think we made clear enough how to use this non-default configuration and its advantages for users to go out of their ways to use it.