From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH] virtio-spec: balloon: MUST_TELL_HOST is optional Date: Wed, 19 Jun 2013 12:25:47 +0930 Message-ID: <87wqpqn70s.fsf@rustcorp.com.au> References: <20120909113650.GA2775@redhat.com> <20121112170308.GB18220@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121112170308.GB18220@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, pbonzini@redhat.com List-Id: virtualization@lists.linuxfoundation.org "Michael S. Tsirkin" writes: > On Sun, Sep 09, 2012 at 02:36:50PM +0300, Michael S. Tsirkin wrote: >> Drivers treat MUST_TELL_HOST as optional: windows drivers do not ack it >> and expect this means they can tell host *after* deflate. This was not >> the intent but the documentation was not very clear on this point. >> >> Luckily hyprevisors did not implement this feature yet so to provide >> guidance for future devices make spec match drivers expectations, and >> clarify that this feature only has effect if negotiated. >> This is needed as recent developments in kvm (memory >> region rework and the addition of vfio) finally make >> it practical to implement this in devices. >> >> Signed-off-by: Michael S. Tsirkin > > Acked-by: Paolo Bonzini > > ping OK, I just s/set/negotiated: --- virtio-spec.txt.old 2013-06-17 16:03:51.875066122 +0930 +++ virtio-spec.txt 2013-06-17 16:07:42.291063924 +0930 @@ -2411,9 +2411,9 @@ it has previously given to the balloon, as described above. This descriptor is added to the deflateq. - (b) If the VIRTIO_BALLOON_F_MUST_TELL_HOST feature is set, the - guest may not use these requested pages until that descriptor - in the deflateq has been used by the device. + (b) If the VIRTIO_BALLOON_F_MUST_TELL_HOST feature is + negotiated, the guest may not use these requested pages until + that descriptor in the deflateq has been used by the device. (c) Otherwise, the guest may begin to re-use pages previously given to the balloon before the device has acknowledged their I'm think we get rid of the output queue for balloon in future. Cheers, Rusty.