Re: [Qemu-devel] [PATCH v3 00/29] postcopy+vhost-user/shared ram

[Dr. David Alan Gilbert]

* Michael S. Tsirkin (address@hidden) wrote:
> On Fri, Feb 16, 2018 at 01:15:56PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> > 
> > Hi,
> >   This is the first non-RFC version of this patch set that
> > enables postcopy migration with shared memory to a vhost user process.
> > It's based off current head.
> > 
> > I've tested with vhost-user-bridge and a modified dpdk; both very
> > lightly.
> > 
> > Compared to v2 we're now using the just-merged reworks to the vhost
> > code (suggested by Igor), so that the huge page region merging is now a lot 
> > simpler
> > in this series. The handshake between the client and the qemu for the
> > set-mem-table is now a bit more complex to resolve a previous race where
> > the client would start sending requests to the qemu prior to the qemu
> > being ready to accept them.
> > 
> > Dave
> 
> From vhost-user POV this seems mostly fine to me.

OK, great - it would be nice to get this merged in the upcoming release
(Hint: Anyone else please review!)

> I would like to have dependency of specific messages on the
> protocol features documented, and the order of messages
> documented a bit more explicitly.

Something like the following? (appropriately merged in with the
individual commits):

diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
index 4bf7d8ef99..7841812766 100644
--- a/docs/interop/vhost-user.txt
+++ b/docs/interop/vhost-user.txt
@@ -461,7 +461,7 @@ Master message types
       for each memory mapped region. The size and ordering of the fds matches
       the number and ordering of memory regions.
 
-      When postcopy-listening has been received, SET_MEM_TABLE replies with
+      When VHOST_USER_POSTCOPY_LISTEN has been received, SET_MEM_TABLE replies 
with
       the bases of the memory mapped regions to the master.  It must have 
mmap'd
       the regions but not yet accessed them and should not yet generate a 
userfault
       event. Note NEED_REPLY_MASK is not set in this case.
@@ -687,7 +687,8 @@ Master message types
       Master payload: N/A
       Slave payload: userfault fd + u64
 
-      Master advises slave that a migration with postcopy enabled is underway,
+      When VHOST_USER_PROTOCOL_F_PAGEFAULT is supported, the
+      master advises slave that a migration with postcopy enabled is underway,
       the slave must open a userfaultfd for later use.
       Note that at this stage the migration is still in precopy mode.
 
@@ -696,6 +697,8 @@ Master message types
       Master payload: N/A
 
       Master advises slave that a transition to postcopy mode has happened.
+      This is always sent sometime after a VHOST_USER_POSTCOPY_ADVISE, and
+      thus only when VHOST_USER_PROTOCOL_F_PAGEFAULT is supported.
 
  * VHOST_USER_POSTCOPY_END
       Id: 28
@@ -704,6 +707,8 @@ Master message types
       Master advises that postcopy migration has now completed.  The
       slave must disable the userfaultfd. The response is an acknowledgement
       only.
+      This message is sent at the end of the migration, after
+      VHOST_USER_POSTCOPY_LISTEN was previously sent.
 
 Slave message types
 -------------------

Dave

> 
> 
> 
> > Dr. David Alan Gilbert (29):
> >   migrate: Update ram_block_discard_range for shared
> >   qemu_ram_block_host_offset
> >   postcopy: use UFFDIO_ZEROPAGE only when available
> >   postcopy: Add notifier chain
> >   postcopy: Add vhost-user flag for postcopy and check it
> >   vhost-user: Add 'VHOST_USER_POSTCOPY_ADVISE' message
> >   libvhost-user: Support sending fds back to qemu
> >   libvhost-user: Open userfaultfd
> >   postcopy: Allow registering of fd handler
> >   vhost+postcopy: Register shared ufd with postcopy
> >   vhost+postcopy: Transmit 'listen' to client
> >   postcopy+vhost-user: Split set_mem_table for postcopy
> >   migration/ram: ramblock_recv_bitmap_test_byte_offset
> >   libvhost-user+postcopy: Register new regions with the ufd
> >   vhost+postcopy: Send address back to qemu
> >   vhost+postcopy: Stash RAMBlock and offset
> >   vhost+postcopy: Send requests to source for shared pages
> >   vhost+postcopy: Resolve client address
> >   postcopy: wake shared
> >   postcopy: postcopy_notify_shared_wake
> >   vhost+postcopy: Add vhost waker
> >   vhost+postcopy: Call wakeups
> >   libvhost-user: mprotect & madvises for postcopy
> >   vhost-user: Add VHOST_USER_POSTCOPY_END message
> >   vhost+postcopy: Wire up POSTCOPY_END notify
> >   vhost: Huge page align and merge
> >   postcopy: Allow shared memory
> >   libvhost-user: Claim support for postcopy
> >   postcopy shared docs
> > 
> >  contrib/libvhost-user/libvhost-user.c | 303 ++++++++++++++++++++++++-
> >  contrib/libvhost-user/libvhost-user.h |   8 +
> >  docs/devel/migration.rst              |  41 ++++
> >  docs/interop/vhost-user.txt           |  42 ++++
> >  exec.c                                |  85 +++++--
> >  hw/virtio/trace-events                |  16 +-
> >  hw/virtio/vhost-user.c                | 411 
> > +++++++++++++++++++++++++++++++++-
> >  hw/virtio/vhost.c                     |  66 +++++-
> >  include/exec/cpu-common.h             |   4 +
> >  migration/migration.c                 |   6 +
> >  migration/migration.h                 |   4 +
> >  migration/postcopy-ram.c              | 350 +++++++++++++++++++++++------
> >  migration/postcopy-ram.h              |  69 ++++++
> >  migration/ram.c                       |   5 +
> >  migration/ram.h                       |   1 +
> >  migration/savevm.c                    |  13 ++
> >  migration/trace-events                |   6 +
> >  trace-events                          |   3 +-
> >  vl.c                                  |   2 +
> >  19 files changed, 1337 insertions(+), 98 deletions(-)
> > 
> > -- 
> > 2.14.3
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK