Re: [Qemu-devel] [v1 Patch 0/10]Qemu: Dynamic host pagecache change and image file reopen

2012-07-09 Thread Stefan Weil 

Am 15.06.2012 22:46, schrieb Supriya Kannery:

  For changing host pagecache setting of a running VM, it is
important to have a safe way of reopening its image file.




Hello,

please use 'QEMU' instead of 'Qemu' where needed.

I assume that everybody here expects that any patch
on this mailing list is for QEMU, so there is no need
to start the summaries of indiviual patches with
QEMU:. You could start them with block: or take
a look in the files' history to see what other people
used.

Regards

Stefan Weil

[Qemu-devel] [v1 Patch 0/10]Qemu: Dynamic host pagecache change and image file reopen

2012-06-15 Thread Supriya Kannery 
 For changing host pagecache setting of a running VM, it is
important to have a safe way of reopening its image file.

Following patchset introduces:
 * a generic way to reopen image files safely. 
In this approach, before reopening an image, for each
block driver, its state will be stashed. Incase preparation,
(bdrv_reopen_prepare) for reopening returns success, the stashed 
state will be cleared (bdrv_reopen_commit) and reopened state will 
be used further. Incase preparation of reopening returns failure, 
the state of the driver will be rolled back (bdrv_reopen_abort) 
to the stashed state. This approach is implemented for raw-posix, 
raw-win32, vmdk, qcow, qcow2 and qed block drivers.
  
 * qmp and hmp command 'block_set_hostcache' using which host 
   pagecache setting for a block device can be changed 
   when the VM is running.

 * BDRVReopenState, a generic structure which can be 
   extended by each of the block drivers to reopen 
   respective image files.

ToDo:
* Currently driver state is stashed by field-by-field copy.
  Optimise this by stashing only the required fields.
* Find out other drivers needing bdrv_reopen implementation.
* Do some more extensive testing, especially with drivers like
  floppy, cdrom etc..

Earlier discussions on RFC for dynamic change of host pagecache can be
 found at: http://lists.gnu.org/archive/html/qemu-devel/2012-01/msg04139.html

New block command added:
block_set_hostcache
-- Sets hostcache parameter for block device  while guest is running.

Usage:
 block_set_hostcache  device option
   device = block device
   option  = on/off

 qemu/block.c   |  127 --
 qemu/block.h   |5 +
 qemu/block/qcow.c  |  108 +
 qemu/block/qcow2.c |  177 +
 qemu/block/qed.c   |  103 
 qemu/block/raw-posix.c |  123 ++
 qemu/block/raw-win32.c |   96 ++
 qemu/block/raw.c   |   20 +
 qemu/block/vmdk.c  |  103 
 qemu/block_int.h   |   11 +++
 qemu/blockdev.c|   24 ++
 qemu/hmp-commands.hx   |   16 
 qemu/hmp.c |   11 ++
 qemu/hmp.h |1
 qemu/qapi-schema.json  |   20 -
 qemu/qemu-common.h |1
 qemu/qerror.c  |8 ++
 qemu/qerror.h  |6 +
 qemu/qmp-commands.hx   |   24 ++
 19 files changed, 971 insertions(+), 13 deletions(-)