From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: John G Johnson <john.g.johnson@oracle.com>
Cc: "Elena Ufimtseva" <elena.ufimtseva@oracle.com>,
"fam@euphon.net" <fam@euphon.net>,
"Swapnil Ingle" <swapnil.ingle@nutanix.com>,
"mst@redhat.com" <mst@redhat.com>,
"Stefan Hajnoczi" <stefanha@gmail.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Walker, Benjamin" <benjamin.walker@intel.com>,
"kraxel@redhat.com" <kraxel@redhat.com>,
"jag.raman@oracle.com" <jag.raman@oracle.com>,
"Harris, James R" <james.r.harris@intel.com>,
"quintela@redhat.com" <quintela@redhat.com>,
"armbru@redhat.com" <armbru@redhat.com>,
"kanth.ghatraju@oracle.com" <kanth.ghatraju@oracle.com>,
"Felipe Franciosi" <felipe@nutanix.com>,
"thuth@redhat.com" <thuth@redhat.com>,
"ehabkost@redhat.com" <ehabkost@redhat.com>,
"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
"liran.alon@oracle.com" <liran.alon@oracle.com>,
"Thanos Makatos" <thanos.makatos@nutanix.com>,
"rth@twiddle.net" <rth@twiddle.net>,
"kwolf@redhat.com" <kwolf@redhat.com>,
"\"Daniel P. Berrangé\"" <berrange@redhat.com>,
"mreitz@redhat.com" <mreitz@redhat.com>,
"ross.lagerwall@citrix.com" <ross.lagerwall@citrix.com>,
"marcandre.lureau@gmail.com" <marcandre.lureau@gmail.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>
Subject: Re: [RFC v4 PATCH 00/49] Initial support of multi-process qemu - status update
Date: Fri, 17 Jan 2020 17:25:26 +0000 [thread overview]
Message-ID: <20200117172526.GQ3209@work-vm> (raw)
In-Reply-To: <39A027D6-21C3-484F-8F90-9F04DCB9E4CF@oracle.com>
* John G Johnson (john.g.johnson@oracle.com) wrote:
<snip>
> DMA
>
> This is one place where I might diverge from VFIO. It uses an
> ioctl to tell the kernel driver what areas of guest memory the device
> can address. The driver then pins that memory so it can be programmed
> into a HW IOMMU. We could avoid pinning of guest memory by adopting
> the vhost-user idea of sending the file descriptors used by QEMU to
> create guest memory to the emulation process, and having it mmap() the
> guest itself. IOMMUs are handled by having the emulation process
> request device DMA to guest PA translations from QEMU.
The interface in vhost-user to pass these memory fd's is a bit hairy;
so it would be great if there was something better for multi-process.
Some things to think about:
a) vhost-user filters it so that areas of memory not backed by an fd
aren't passed to the client; this filters out some of the device
specific RAM blocks that aren't really normal RAM.
b) Hugepages are tricky; especially on a PC where the 0-1MB area is
broken up into chunks and you're trying to mmap 2MB chunks into the
client.
c) Postcopy with vhost-user was pretty tricky as well; there needs
to be some coordination with the qemu to handle pages that are missing.
d) Some RAM mappings can change; mostly not the ones sent to the
client; but just watch out that these can happen at unexpected times.
Dave
>
>
> > If implementations can use the kernel uapi vfio header files then we're
> > on track for compatibility with VFIO.
> >
> >>> This is just a more elaborate explanation for the "the cat is out of the
> >>> bag" comments that have already been made on licensing. Does anyone
> >>> still disagree or want to discuss further?
> >>>
> >>> If there is agreement that a stable API is okay then I think the
> >>> practical way to do this is to first merge a cleaned-up version of
> >>> multi-process QEMU as an unstable experimental API. Once it's being
> >>> tested and used we can write a protocol specification and publish it as
> >>> a stable interface when the spec has addressed most use cases.
> >>>
> >>> Does this sound good?
> >>
> >> In that case, wouldn't it be preferable to revive our proposal from
> >> Edinburgh (KVM Forum 2018)? Our prototypes moved more of the Qemu VFIO
> >> code to "common" and added a "user" backend underneath it, similar to
> >> how vhost-user-scsi moved some of vhost-scsi to vhost-scsi-common and
> >> added vhost-user-scsi. It was centric on PCI, but it doesn't have to
> >> be. The other side can be implemented in libmuser for facilitating things.
> >
> > That sounds good.
> >
>
> The emulation program API could be based on the current
> libmuser API or the libvfio-user API. The protocol itself wouldn’t
> care which is chosen. Our multi-processQEMU project would have to
> change how devices are specified from the QEMU command line to the
> emulation process command line.
>
> JJ
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2020-01-17 17:26 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-24 9:08 [RFC v4 PATCH 00/49] Initial support of multi-process qemu Jagannathan Raman
2019-10-24 9:08 ` [RFC v4 PATCH 01/49] multi-process: memory: alloc RAM from file at offset Jagannathan Raman
2019-10-24 9:08 ` [RFC v4 PATCH 02/49] multi-process: util: Add qemu_thread_cancel() to cancel running thread Jagannathan Raman
2019-11-13 15:30 ` Stefan Hajnoczi
2019-11-13 15:38 ` Jag Raman
2019-11-13 15:51 ` Daniel P. Berrangé
2019-11-13 16:04 ` Jag Raman
2019-11-13 16:35 ` Daniel P. Berrangé
2019-10-24 9:08 ` [RFC v4 PATCH 03/49] multi-process: add a command line option for debug file Jagannathan Raman
2019-11-13 15:35 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 04/49] multi-process: Add stub functions to facilate build of multi-process Jagannathan Raman
2019-10-24 9:08 ` [RFC v4 PATCH 05/49] multi-process: Add config option for multi-process QEMU Jagannathan Raman
2019-10-24 9:08 ` [RFC v4 PATCH 06/49] multi-process: build system for remote device process Jagannathan Raman
2019-10-24 9:08 ` [RFC v4 PATCH 07/49] multi-process: define mpqemu-link object Jagannathan Raman
2019-11-11 16:41 ` Stefan Hajnoczi
2019-11-13 15:47 ` Jag Raman
2019-11-13 15:53 ` Stefan Hajnoczi
2019-11-18 15:26 ` Jag Raman
2019-10-24 9:08 ` [RFC v4 PATCH 08/49] multi-process: add functions to synchronize proxy and remote endpoints Jagannathan Raman
2019-10-24 9:08 ` [RFC v4 PATCH 09/49] multi-process: setup PCI host bridge for remote device Jagannathan Raman
2019-11-13 16:07 ` Stefan Hajnoczi
2019-11-18 15:25 ` Jag Raman
2019-11-21 10:37 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 10/49] multi-process: setup a machine object for remote device process Jagannathan Raman
2019-11-13 16:22 ` Stefan Hajnoczi
2019-11-18 15:29 ` Jag Raman
2019-10-24 9:08 ` [RFC v4 PATCH 11/49] multi-process: setup memory manager for remote device Jagannathan Raman
2019-11-13 16:33 ` Stefan Hajnoczi
2019-11-13 16:34 ` Jag Raman
2019-10-24 9:08 ` [RFC v4 PATCH 12/49] multi-process: remote process initialization Jagannathan Raman
2019-11-13 16:38 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 13/49] multi-process: introduce proxy object Jagannathan Raman
2019-11-21 11:09 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 14/49] mutli-process: build remote command line args Jagannathan Raman
2019-11-21 11:23 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 15/49] multi-process: PCI BAR read/write handling for proxy & remote endpoints Jagannathan Raman
2019-11-21 11:33 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 16/49] multi-process: Add LSI device proxy object Jagannathan Raman
2019-11-21 11:35 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 17/49] multi-process: Synchronize remote memory Jagannathan Raman
2019-11-21 11:44 ` Stefan Hajnoczi
2019-10-24 9:08 ` [RFC v4 PATCH 18/49] multi-process: create IOHUB object to handle irq Jagannathan Raman
2019-11-21 12:02 ` Stefan Hajnoczi
2019-10-24 9:09 ` [RFC v4 PATCH 19/49] multi-process: configure remote side devices Jagannathan Raman
2019-11-21 12:05 ` Stefan Hajnoczi
2019-10-24 9:09 ` [RFC v4 PATCH 20/49] multi-process: add qdev_proxy_add to create proxy devices Jagannathan Raman
2019-11-21 12:16 ` Stefan Hajnoczi
2019-10-24 9:09 ` [RFC v4 PATCH 21/49] multi-process: remote: add setup_devices and setup_drive msg processing Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 22/49] multi-process: remote: use fd for socket from parent process Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 23/49] multi-process: remote: add create_done condition Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 24/49] multi-process: add processing of remote drive and device command line Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 25/49] multi-process: Introduce build flags to separate remote process code Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 26/49] multi-process: refractor vl.c code to re-use in remote Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 27/49] multi-process: add remote option Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 28/49] multi-process: add remote options parser Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 29/49] multi-process: add parse_cmdline in remote process Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 30/49] multi-process: send heartbeat messages to remote Jagannathan Raman
2019-11-11 16:27 ` Stefan Hajnoczi
2019-11-13 16:01 ` Jag Raman
2019-11-21 12:19 ` Stefan Hajnoczi
2019-10-24 9:09 ` [RFC v4 PATCH 31/49] multi-process: handle heartbeat messages in remote process Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 32/49] multi-process: Use separate MMIO communication channel Jagannathan Raman
2019-11-11 16:21 ` Stefan Hajnoczi
2019-11-13 16:14 ` Jag Raman
2019-11-21 12:31 ` Stefan Hajnoczi
2019-10-24 9:09 ` [RFC v4 PATCH 33/49] multi-process: perform device reset in the remote process Jagannathan Raman
2019-11-11 16:19 ` Stefan Hajnoczi
2019-11-13 16:15 ` Jag Raman
2019-10-24 9:09 ` [RFC v4 PATCH 34/49] multi-process/mon: choose HMP commands based on target Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 35/49] multi-process/mon: stub functions to enable QMP module for remote process Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 36/49] multi-process/mon: enable QMP module support in the " Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 37/49] multi-process/mon: Refactor monitor/chardev functions out of vl.c Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 38/49] multi-process/mon: Initialize QMP module for remote processes Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 39/49] multi-process: prevent duplicate memory initialization in remote Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 40/49] multi-process/mig: build migration module in the remote process Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 41/49] multi-process/mig: Enable VMSD save in the Proxy object Jagannathan Raman
2019-11-13 15:50 ` Daniel P. Berrangé
2019-11-13 16:32 ` Jag Raman
2019-11-13 17:11 ` Daniel P. Berrangé
2019-11-18 15:42 ` Jag Raman
2019-11-22 10:34 ` Dr. David Alan Gilbert
2019-10-24 9:09 ` [RFC v4 PATCH 42/49] multi-process/mig: Send VMSD of remote to " Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 43/49] multi-process/mig: Load VMSD in the proxy object Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 44/49] multi-process/mig: refactor runstate_check into common file Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 45/49] multi-process/mig: Synchronize runstate of remote process Jagannathan Raman
2019-11-11 16:17 ` Stefan Hajnoczi
2019-11-13 16:33 ` Jag Raman
2019-10-24 9:09 ` [RFC v4 PATCH 46/49] multi-process/mig: Restore the VMSD in " Jagannathan Raman
2019-10-24 9:09 ` [RFC v4 PATCH 47/49] multi-process: Enable support for multiple devices in remote Jagannathan Raman
2019-11-11 16:15 ` Stefan Hajnoczi
2019-11-13 16:21 ` Jag Raman
2019-10-24 9:09 ` [RFC v4 PATCH 48/49] multi-process: add the concept description to docs/devel/qemu-multiprocess Jagannathan Raman
2019-10-25 19:33 ` Elena Ufimtseva
2019-11-07 15:50 ` Stefan Hajnoczi
2019-11-11 15:41 ` Stefan Hajnoczi
2019-10-24 9:09 ` [RFC v4 PATCH 49/49] multi-process: add configure and usage information Jagannathan Raman
2019-11-07 14:02 ` Stefan Hajnoczi
2019-11-07 14:33 ` Michael S. Tsirkin
2019-11-08 11:17 ` Stefan Hajnoczi
2019-11-08 11:32 ` Daniel P. Berrangé
2019-11-07 14:39 ` Daniel P. Berrangé
2019-11-07 15:53 ` Jag Raman
2019-11-08 11:14 ` Stefan Hajnoczi
2019-10-25 2:08 ` [RFC v4 PATCH 00/49] Initial support of multi-process qemu no-reply
2019-10-25 2:08 ` no-reply
2019-10-25 2:10 ` no-reply
2019-11-21 12:46 ` Stefan Hajnoczi
2019-12-10 6:47 ` [RFC v4 PATCH 00/49] Initial support of multi-process qemu - status update Elena Ufimtseva
2019-12-13 10:41 ` Stefan Hajnoczi
2019-12-16 19:46 ` Elena Ufimtseva
2019-12-16 19:57 ` Felipe Franciosi
2019-12-17 16:33 ` Stefan Hajnoczi
2019-12-17 22:57 ` Felipe Franciosi
2019-12-18 0:00 ` Paolo Bonzini
2019-12-19 13:36 ` Stefan Hajnoczi
2019-12-20 17:15 ` John G Johnson
2020-01-02 10:00 ` Stefan Hajnoczi
2020-01-02 10:04 ` Stefan Hajnoczi
2019-12-19 11:55 ` Stefan Hajnoczi
2019-12-19 12:33 ` Felipe Franciosi
2019-12-19 12:55 ` Daniel P. Berrangé
2019-12-20 9:47 ` Stefan Hajnoczi
2019-12-20 9:50 ` Paolo Bonzini
2019-12-20 14:14 ` Felipe Franciosi
2019-12-20 15:25 ` Alex Williamson
2019-12-20 16:00 ` Felipe Franciosi
2020-02-25 9:16 ` Thanos Makatos
2019-12-20 10:22 ` Daniel P. Berrangé
2020-01-02 10:42 ` Stefan Hajnoczi
2020-01-02 11:03 ` Felipe Franciosi
2020-01-02 18:55 ` Marc-André Lureau
2020-01-08 16:31 ` Stefan Hajnoczi
2020-01-03 15:59 ` Stefan Hajnoczi
2020-01-14 1:56 ` John G Johnson
2020-01-17 17:25 ` Dr. David Alan Gilbert [this message]
2019-12-19 16:40 ` Jag Raman
2019-12-19 12:50 ` Daniel P. Berrangé
2019-12-19 16:46 ` Daniel P. Berrangé
2020-01-02 16:01 ` Elena Ufimtseva
2020-01-03 15:00 ` Stefan Hajnoczi
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