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Wed, 19 Aug 2020 08:00:03 +0000 (UTC) Date: Wed, 19 Aug 2020 09:00:01 +0100 From: Stefan Hajnoczi To: Elena Ufimtseva Subject: Re: [PATCH v8 17/20] multi-process: heartbeat messages to remote Message-ID: <20200819080001.GA334045@stefanha-x1.localdomain> References: <93b7566e5d565b9e5d8127849bb5be65057e25cc.1596217462.git.jag.raman@oracle.com> <20200811144130.GC18223@stefanha-x1.localdomain> <20200814230147.GA177362@heatpipe> MIME-Version: 1.0 In-Reply-To: <20200814230147.GA177362@heatpipe> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="7AUc2qLy4jB3hD7Z" Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=stefanha@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 04:00:34 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fam@euphon.net, john.g.johnson@oracle.com, swapnil.ingle@nutanix.com, mst@redhat.com, qemu-devel@nongnu.org, kraxel@redhat.com, Jagannathan Raman , quintela@redhat.com, armbru@redhat.com, kanth.ghatraju@oracle.com, felipe@nutanix.com, thuth@redhat.com, ehabkost@redhat.com, konrad.wilk@oracle.com, dgilbert@redhat.com, alex.williamson@redhat.com, thanos.makatos@nutanix.com, rth@twiddle.net, kwolf@redhat.com, berrange@redhat.com, mreitz@redhat.com, ross.lagerwall@citrix.com, marcandre.lureau@gmail.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --7AUc2qLy4jB3hD7Z Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 14, 2020 at 04:01:47PM -0700, Elena Ufimtseva wrote: > On Tue, Aug 11, 2020 at 03:41:30PM +0100, Stefan Hajnoczi wrote: > > On Fri, Jul 31, 2020 at 02:20:24PM -0400, Jagannathan Raman wrote: > > > @@ -343,3 +349,49 @@ static void probe_pci_info(PCIDevice *dev, Error= **errp) > > > } > > > } > > > } > > > + > > > +static void hb_msg(PCIProxyDev *dev) > > > +{ > > > + DeviceState *ds =3D DEVICE(dev); > > > + Error *local_err =3D NULL; > > > + MPQemuMsg msg =3D { 0 }; > > > + > > > + msg.cmd =3D PROXY_PING; > > > + msg.bytestream =3D 0; > > > + msg.size =3D 0; > > > + > > > + (void)mpqemu_msg_send_and_await_reply(&msg, dev->ioc, &local_err= ); > > > + if (local_err) { > > > + error_report_err(local_err); > > > + qio_channel_close(dev->ioc, &local_err); > > > + error_setg(&error_fatal, "Lost contact with device %s", ds->= id); > > > + } > > > +} > >=20 > > Here is my feedback from the last revision. Was this addressed? > > >=20 > Hi Stefan, >=20 > Thank you for reviewing the patchset. In this version we decided to=20 > shutdown the guest when the heartbeat did not get a reply from the > remote by setting the error_fatal. > Should we approach it differently or you prefer us to get rid of the > heartbeat in this form? I think the only case that this patch handles is when the mpqemu channel is closed. The VM hangs when the channel is still open but the remote is unresponsive. (mpqemu_msg_send_and_await_reply() calls aio_poll() with the global mutex held so vcpus cannot make progress.) The heartbeat mechanism needs to handle the case where the other side isn't responding. It can't hang QEMU. I suggest dropping this patch. It can be done later. 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