From: Stefan Hajnoczi <stefanha@redhat.com>
To: Jagannathan Raman <jag.raman@oracle.com>
Cc: elena.ufimtseva@oracle.com, fam@euphon.net,
swapnil.ingle@nutanix.com, john.g.johnson@oracle.com,
qemu-devel@nongnu.org, kraxel@redhat.com, quintela@redhat.com,
mst@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: Tue, 11 Aug 2020 15:41:30 +0100 [thread overview]
Message-ID: <20200811144130.GC18223@stefanha-x1.localdomain> (raw)
In-Reply-To: <93b7566e5d565b9e5d8127849bb5be65057e25cc.1596217462.git.jag.raman@oracle.com>
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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?
This patch seems incomplete since no action is taken when the device
fails to respond. vCPU threads that access the device will still get
stuck.
The simplest way to make this useful is to close the connection when a
timeout occurs. Then the G_IO_HUP handler for the UNIX domain socket
should perform connection cleanup. At that point there are a few
choices:
1. Stop guest execution and wait for the host admin to restore the
mplink so execution can resume. This is similar to how -drive
rerror=stop pauses the guest when a disk I/O error is encountered.
2. Stop guest execution but defer it until this stale device is actually
accessed. This maximizes guest uptime. Guests that rarely access the
device may not notice at all.
3. Return 0 from MemoryRegion read operations and ignore writes. The
guest continues executing but the device is broken. This is risky
because device drivers inside the guest may not be ready to deal with
this. The result could be data loss or corruption.
4. Raise a bus-level event. Maybe PCI error reporting can be used to
offline the device.
5. Terminate the guest with an error message.
6. ?
Until the heartbeat is fully implemented and tested I suggest dropping
it from this patch series. Remember the G_IO_HUP will happen anyway if
the remote device process terminates.
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next prev parent reply other threads:[~2020-08-11 14:42 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 [this message]
2020-08-14 23:01 ` Elena Ufimtseva
2020-08-19 8:00 ` Stefan Hajnoczi
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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