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From: Stefan Hajnoczi <stefanha@redhat.com>
To: Elena Ufimtseva <elena.ufimtseva@oracle.com>
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 <jag.raman@oracle.com>,
	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
Subject: Re: [PATCH v8 17/20] multi-process: heartbeat messages to remote
Date: Wed, 19 Aug 2020 09:00:01 +0100	[thread overview]
Message-ID: <20200819080001.GA334045@stefanha-x1.localdomain> (raw)
In-Reply-To: <20200814230147.GA177362@heatpipe>

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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 = DEVICE(dev);
> > > +    Error *local_err = NULL;
> > > +    MPQemuMsg msg = { 0 };
> > > +
> > > +    msg.cmd = PROXY_PING;
> > > +    msg.bytestream = 0;
> > > +    msg.size = 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);
> > > +    }
> > > +}
> > 
> > Here is my feedback from the last revision. Was this addressed?
> >
> 
> Hi Stefan,
> 
> Thank you for reviewing the patchset. In this version we decided to 
> 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.

Stefan

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  reply	other threads:[~2020-08-19  8:01 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 18:20 [PATCH v8 00/20] Initial support for multi-process qemu Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 01/20] memory: alloc RAM from file at offset Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 02/20] multi-process: Add config option for multi-process QEMU Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 03/20] multi-process: setup PCI host bridge for remote device Jagannathan Raman
2020-08-04 10:47   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 04/20] multi-process: setup a machine object for remote device process Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 05/20] multi-process: add qio channel function to transmit Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 06/20] multi-process: define MPQemuMsg format and transmission functions Jagannathan Raman
2020-08-04 12:49   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 07/20] multi-process: add co-routines to communicate with remote Jagannathan Raman
2020-08-10 16:02   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 08/20] multi-process: Initialize message handler in remote device Jagannathan Raman
2020-08-04 12:58   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 09/20] multi-process: Associate fd of a PCIDevice with its object Jagannathan Raman
2020-08-07 16:02   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 10/20] multi-process: setup memory manager for remote device Jagannathan Raman
2020-08-10 15:27   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 11/20] multi-process: introduce proxy object Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 12/20] multi-process: Forward PCI config space acceses to the remote process Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 13/20] multi-process: PCI BAR read/write handling for proxy & remote endpoints Jagannathan Raman
2020-08-11 14:04   ` Stefan Hajnoczi
2020-07-31 18:20 ` [PATCH v8 14/20] multi-process: Synchronize remote memory Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 15/20] multi-process: create IOHUB object to handle irq Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 16/20] multi-process: Retrieve PCI info from remote process Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 17/20] multi-process: heartbeat messages to remote Jagannathan Raman
2020-08-11 14:41   ` Stefan Hajnoczi
2020-08-14 23:01     ` Elena Ufimtseva
2020-08-19  8:00       ` Stefan Hajnoczi [this message]
2020-07-31 18:20 ` [PATCH v8 18/20] multi-process: perform device reset in the remote process Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 19/20] multi-process: add the concept description to docs/devel/qemu-multiprocess Jagannathan Raman
2020-07-31 18:20 ` [PATCH v8 20/20] multi-process: add configure and usage information Jagannathan Raman
2020-08-11 14:56 ` [PATCH v8 00/20] Initial support for multi-process qemu Stefan Hajnoczi

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