From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH (repost) RFC 2/2] virtio-pci: recall and return msix notifications on ISR read Date: Thu, 03 Nov 2011 12:42:55 +0100 Message-ID: <4EB27E3F.2030503@siemens.com> References: <6dc9aa9764b1cfddf557a98f269e0f7d31ce03ac.1320259840.git.mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <6dc9aa9764b1cfddf557a98f269e0f7d31ce03ac.1320259840.git.mst@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" Cc: Anthony Liguori , "qemu-devel@nongnu.org" , "virtualization@lists.linux-foundation.org" , Blue Swirl , Stefan Weil , Avi Kivity , Richard Henderson List-Id: virtualization@lists.linuxfoundation.org On 2011-11-02 21:11, Michael S. Tsirkin wrote: > MSIX spec requires that device can be operated with > all vectors masked, by polling pending bits. > Add APIs to recall an msix notification, and make polling > mode possible in virtio-pci by clearing the > pending bits and setting ISR appropriately on ISR read. > > Signed-off-by: Michael S. Tsirkin > --- > hw/msix.c | 26 ++++++++++++++++++++++++++ > hw/msix.h | 3 +++ > hw/virtio-pci.c | 11 ++++++++++- > 3 files changed, 39 insertions(+), 1 deletions(-) > > diff --git a/hw/msix.c b/hw/msix.c > index 63b41b9..fe967c9 100644 > --- a/hw/msix.c > +++ b/hw/msix.c > @@ -349,6 +349,32 @@ void msix_notify(PCIDevice *dev, unsigned vector) > stl_le_phys(address, data); > } > > +/* Recall outstanding MSI-X notifications for a vector, if possible. > + * Return true if any were outstanding. */ > +bool msix_recall(PCIDevice *dev, unsigned vector) > +{ > + bool ret; > + if (vector >= dev->msix_entries_nr) > + return false; > + ret = msix_is_pending(dev, vector); > + msix_clr_pending(dev, vector); > + return ret; > +} I would prefer to have a single API instead to clarify the tight relation: bool msi[x]_set_notify(PCIDevice *dev, unsigned vector, unsigned level) Would return true for level=1 if the message was either sent directly or queued (we could deliver false if it was already queued, but I see no use case for this yet). Also, I don't see the generic value of some msix_recall_all. I think it's better handled in a single loop over all vectors at caller site, clearing the individual interrupt reason bits on a per-vector basis there. msix_recall_all is only useful in the virtio case where you have one vector of reason A and all the rest of B. Once you had multiple reason C vectors as well, it would not help anymore. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux