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postcopy: Add vhost-user flag for postcopy and check it

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Add a vhost feature flag for postcopy support, and
use the postcopy notifier to check it before allowing postcopy.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2018-03-12 17:21:00 +00:00 • committed by Michael S. Tsirkin
parent 1693c64c27
commit 9ccbfe14dd
3 changed files with 52 additions and 1 deletions
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10
docs/interop/vhost-user.txt
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@ -290,6 +290,15 @@ Once the source has finished migration, rings will be stopped by
the source. No further update must be done before rings are
restarted.
In postcopy migration the slave is started before all the memory has been
received from the source host, and care must be taken to avoid accessing pages
that have yet to be received. The slave opens a 'userfault'-fd and registers
the memory with it; this fd is then passed back over to the master.
The master services requests on the userfaultfd for pages that are accessed
and when the page is available it performs WAKE ioctl's on the userfaultfd
to wake the stalled slave. The client indicates support for this via the
VHOST_USER_PROTOCOL_F_PAGEFAULT feature.
Memory access
-------------
@ -369,6 +378,7 @@ Protocol features
#define VHOST_USER_PROTOCOL_F_SLAVE_REQ 5
#define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6
#define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7
#define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
Master message types
--------------------