[Qemu-devel] [V4 Patch 0/4]Qemu: Hostcache setting from cmdline and monitor

[Supriya Kannery]

  Currently cache setting of a block device cannot be changed 
without restarting a running VM. Following patchset is for 
enabling dynamic change of cache setting for block devices 
through qemu monitor. Code changes are based on patches 
from Christoph Hellwig and Prerna Saxena.

  This patchset introduces monitor command 'block_set'
using which various parameters for block devices can be 
changed dynamically. Dynamic changing of host cache 
setting is implemented for now. This patchset also 
introduces 'hostcache', a new option for setting host
cache from qemu command line. 'Hostcache and 'cache' options 
cannot be used simultaneously from commandline.

Changes from patchset V3:
 1. Added 'hostcache' option to '-drive' commandline option.

New block command added:
"block_set" 
    -- Sets block device parameters while guest is running.
Usage:
 block_set <device> <param> <value> 
   <device> = block device
   <param>  = parameter (say, "hostcache")
   <value>  = on/off

New 'hostcache' option added to -drive:
 -drive [file=file][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
        ....    
"       [,readonly=on|off][,hostcache=on|off]\n"

 1/4 Enhance "info block" to display hostcache setting
 2/4 New error classes for file reopen and device insertion
 3/4 Command "block_set" for dynamic params change for block device
 4/4 'hostcache' option added to -drive in qemu commandline

 qemu/block.c         |   73 +++++++++++++++++++++++++++++++++++++++++++++++----
 qemu/block.h         |    2 +
 qemu/blockdev.c      |   43 +++++++++++++++++++++++++++++++++++++++++++++++
 qemu/blockdev.h      |    1
 qemu/hmp-commands.hx |   15 ++++++++++++++
 qemu/qemu-config.c   |    4 +++
 qemu/qemu-options.hx |    2 -
 qemu/qemu.pod        |    5 ++++
 qemu/qerror.c        |    8 +++++++
 qemu/qerror.h        |    6 +++++
 qemu/qmp-commands.hx |   30 +++++++++++++++++++++++++++
 11 files changed, 184 insertions(+), 5 deletions(-)