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Re: [Xen-devel] [PATCH v6 COLO 06/15] libxc/save: support COLO save





On 06/09/2015 04:51 PM, Andrew Cooper wrote:
On 09/06/15 09:45, Yang Hongyang wrote:

Even if there are no dirty pages on secondary, pfn_list shouldn't be
NULL, it's just that pfn_list[0] will be 0. if pfn_list is NULL,
there might be unexpected error happened.

get_dirty_pfn() should be declared alongside a

struct pfn_data
{
      uint64_t count;
      uint64_t *pfns;
};

and this function here should create one of these on the stack and pass
it by pointer to get_dirty_pfn().  I might also be tempted to rename
this to get_remote_logdirty() or similar, to indicate that it is a
source of logdirty data from something other than the current
hypervisor.

This is a callback, I can't find a way to pass pointer from libxc to
libxl,
libxl can not access the pointer data...The struct can be used for
represent
the data however.

Right - my point is that it should be the implementation of
get_remote_logdirty() (i.e. in libxl_save_helper) which is responsible
for unpackaging the data from whatever RPC method is used, rather than
the caller.

Now I know what you mean, I will fix it in the next version, thanks!



Shouldn't get_dirty_pfn be mandatory for COLO streams (even if it is a
noop to start with) ?

It should be mandatory, it shouldn't be noop under COLO. perhaps we
should
add sanity check at the beginning. But problem is save side do not
have a param
passed from libxl to indicate the stream type(like
checkpointed_stream in
restore side). So we may need to add another XCFLAGS? Currently
there is
XCFLAGS_CHECKPOINTED which represents Remus, we might need to change
this to
XCFLAGS_STREAM_REMUS
XCFLAGS_STREAM_COLO
so that we can know what kind of stream we are handling?

checkpointed_stream started out as a bugfix for a legacy stream
migration breakage.  Really, this information should have been passed
right from the start.

Did I miss the bugfix? is it not in upstream?

c/s 7051d5c

Ah, you are talking about the restore side, I'm talking about the save
side checkpointed_stream, so I should also post a prereq patch to
add checkpointed_stream to the save side? or there's already the
fix out there?


~Andrew
.


--
Thanks,
Yang.

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