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Re: [libvirt] [PATCH v2 1/2] make qemu dump memory in kdump-compressed format



On Wed, Feb 26, 2014 at 04:08:11PM +0800, Qiao Nuohan wrote:
> On 02/25/2014 06:56 PM, Jiri Denemark wrote:
> >On Tue, Feb 25, 2014 at 17:54:30 +0800, Qiao Nuohan wrote:
> >>--memory-only option is introduced without compression supported. Therefore,
> >>this is a freature regression of virsh dump. Now qemu has support dumping memory
> >>in kdump-compressed format. This patch is used to add "--compress" and
> >>"[--compression-format]<string>" to "virsh dump --memory-only" and send
> >>dump-guest-memory command to qemu with dump format specified to one of elf,
> >>kdump-zlib, kdump-lzo and kdump-snappy.
> >>
> >>Signed-off-by: Qiao Nuohan<qiaonuohan cn fujitsu com>
> >>---
> >>   include/libvirt/libvirt.h.in | 15 ++++++++++++++-
> >>   src/driver.h                 |  3 ++-
> >>   src/libvirt.c                | 10 ++++++++--
> >>   src/qemu/qemu_driver.c       | 30 +++++++++++++++++++++--------
> >>   src/qemu/qemu_monitor.c      |  6 +++---
> >>   src/qemu/qemu_monitor.h      |  3 ++-
> >>   src/qemu/qemu_monitor_json.c |  4 +++-
> >>   src/qemu/qemu_monitor_json.h |  3 ++-
> >>   src/remote/remote_protocol.x |  1 +
> >>   src/test/test_driver.c       | 12 +++++++++++-
> >>   tests/qemumonitorjsontest.c  |  2 +-
> >>   tools/virsh-domain.c         | 45 +++++++++++++++++++++++++++++++++++++++++++-
> >>   12 files changed, 113 insertions(+), 21 deletions(-)
> >>
> >>diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
> >>index 295d551..aae3c49 100644
> >>--- a/include/libvirt/libvirt.h.in
> >>+++ b/include/libvirt/libvirt.h.in
> >>@@ -1180,6 +1180,18 @@ typedef enum {
> >>       VIR_DUMP_MEMORY_ONLY  = (1<<  4), /* use dump-guest-memory */
> >>   } virDomainCoreDumpFlags;
> >>
> >>+typedef enum {
> >>+    VIR_MEMORY_DUMP_COMPRESS_ZLIB   = 1, /* dump guest memory in
> >>+                                            kdump-compressed format, with
> >>+                                            zlib-compressed */
> >>+    VIR_MEMORY_DUMP_COMPRESS_LZO    = 2, /* dump guest memory in
> >>+                                            kdump-compressed format, with
> >>+                                            lzo-compressed */
> >>+    VIR_MEMORY_DUMP_COMPRESS_SNAPPY = 3, /* dump guest memory in
> >>+                                            kdump-compressed format, with
> >>+                                            snappy-compressed */
> >>+} virMemoryDumpFormat;
> >>+
> >>   /* Domain migration flags. */
> >>   typedef enum {
> >>       VIR_MIGRATE_LIVE              = (1<<  0), /* live migration */
> >>@@ -1728,7 +1740,8 @@ int
> >>virDomainManagedSaveRemove(virDomainPtr dom,
> >>    */
> >>   int                     virDomainCoreDump       (virDomainPtr domain,
> >>                                                    const char *to,
> >>-                                                 unsigned int flags);
> >>+                                                 unsigned int flags,
> >>+                                                 const unsigned int
> >>memory_dump_format);
> >
> >This is not allowed and I believe "make syntax-check" should fail on the
> >corresponding change to remote_protocol.x. If you want to add a new
> >parameter to an existing API, you have keep the API as is and instead
> >create a new API with a different name that will have all the parameters
> >you need.
> 
> Hello Jirka,
> 
> Thanks for pointing it out for me, I finally found it's libvirt's policy never
> to change a committed public API. But driver handling methods are allowed to be
> changed, am I right?

Yes & no. There should be a 1-1 mapping of APIs in libvirt.h to driver
callbacks defined in src/driver.h. The driver.h maps into the remote
RPC protocol and that is considered part of the ABI and thus must not
change.

What is permitted is in the implementation of the new APIs is to share
code with the impl of the old API. ie in qemu_driver.c

Regards,
Daniel
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