From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH] kvm guest balloon driver Date: Tue, 08 Jan 2008 10:43:14 -0600 Message-ID: <4783A822.6000204@codemonkey.ws> References: <20080108153356.GA21726@dmt> <478399D5.9030707@codemonkey.ws> <20080108161005.GA22168@dmt> <4783A14A.3080605@codemonkey.ws> <4783A68E.80901@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm-devel , virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Avi Kivity Return-path: In-Reply-To: <4783A68E.80901-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Avi Kivity wrote: > Anthony Liguori wrote: >> BTW, I don't think the target should be a config value. You don't >> gain anything from it being in the config space and it's somewhat >> unnatural for a virtio device. It makes more sense as a message to >> the guest. >> > > I disagree. The target is state, not an individual item that needs to > be acted on. Having it as a single variable means that multiple > changes are collapsed automatically, and that the the setting survives > module reload. > > It's like a volume control, it doesn't send messages when you turn it, > it just sets a value. It's a value that is meant to be acted upon though, not something to be polled. You want to tell the driver that it should now try to balloon to a certain value. Or maybe not. Maybe the driver should read the target from the config space but then have a "kick" message that tells it, hey, something's probably changed. > (maybe a thermostat knob is a better analogy, with the driver being > the circuitry around the knob that tries to control the temperature to > match the setting) FWIW, I'm pretty sure that most modern volume controls are actually button presses for either direction instead of a variable resistor but point taken ;-) > I believe state-like controls will be useful for other settings, like > ethernet link state. It's difficult with the current config interface since it treats everything as a discrete blob that is updated all at once. I'm not really sure how to proceed. Rusty: do you have an opinion here? Regards, Anthony Liguori ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace