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Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to V
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription |
Date: |
Wed, 17 Oct 2018 14:07:32 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
"Dr. David Alan Gilbert" <address@hidden> wrote:
> * Aaron Lindsay (address@hidden) wrote:
>> On Oct 16 09:21, Dr. David Alan Gilbert wrote:
>> > * Richard Henderson (address@hidden) wrote:
>> > > On 10/10/18 1:37 PM, Aaron Lindsay wrote:
>> > > > In some cases it may be helpful to modify state before saving it for
>> > > > migration, and then modify the state back after it has been saved. The
>> > > > existing pre_save function provides half of this functionality. This
>> > > > patch adds a post_save function to provide the second half.
>> > > >
>> > > > Signed-off-by: Aaron Lindsay <address@hidden>
>> > > > ---
>> > > > docs/devel/migration.rst | 9 +++++++--
>> > > > include/migration/vmstate.h | 1 +
>> > > > migration/vmstate.c | 10 +++++++++-
>> > > > 3 files changed, 17 insertions(+), 3 deletions(-)
>> > >
>> > > Hmm, maybe. I believe the common practice is for pre_save to
>> > > copy state into a
>> > > separate member on the side, so that conversion back isn't necessary.
>> > >
>> > > Ccing in the migration maintainers for a second opinion.
>> >
>> > It is common to copy stuff into a separate member; however we do
>> > occasionally think that post_save would be a useful addition; so I think
>> > we should take it (if nothing else it actually makes stuff symmetric!).
>> >
>> > Please make it return 'int' in the same way that pre_save/pre_load
>> > does, so that it can fail and stop the migration.
>>
>> This patch calls post_save *even if the save operation fails*. My
>> reasoning was that I didn't want a failed migration to leave a
>> still-running original QEMU instance in an invalid state. Was this
>> misguided?
>
> That's fine - my only issue is that I want post_save to be able to fail
> itself even if pre_save failed.
>
>> If it was not, which error do you prefer to be returned from
>> vmstate_save_state_v() in the case that both the save operation itself
>> and the post_save call returned errors?
>
> The return value from the save operation.
> I did wonder about suggesting that you pass the return value from the
> save operation as a parameter to post_save.
The one from save. In general, this one shouldn't be called, and if it
gets an error, we are really in big trouble, no? By big treauble I mean
that we can basically only stop the guest?
Later, Juan.
>
> Dave
>
>> -Aaron
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
- Re: [Qemu-devel] [PATCH v6 08/14] target/arm: Implement PMOVSSET, (continued)
- [Qemu-devel] [PATCH v6 07/14] target/arm: Allow AArch32 access for PMCCFILTR, Aaron Lindsay, 2018/10/10
- [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Aaron Lindsay, 2018/10/10
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Richard Henderson, 2018/10/15
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Dr. David Alan Gilbert, 2018/10/16
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Aaron Lindsay, 2018/10/16
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Dr. David Alan Gilbert, 2018/10/16
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Aaron Lindsay, 2018/10/16
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Dr. David Alan Gilbert, 2018/10/16
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription,
Juan Quintela <=
- Re: [Qemu-devel] [PATCH v6 03/14] migration: Add post_save function to VMStateDescription, Juan Quintela, 2018/10/17
[Qemu-devel] [PATCH v6 09/14] target/arm: Add array for supported PMU events, generate PMCEID[01], Aaron Lindsay, 2018/10/10
[Qemu-devel] [PATCH v6 05/14] target/arm: Reorganize PMCCNTR accesses, Aaron Lindsay, 2018/10/10
Re: [Qemu-devel] [PATCH v6 05/14] target/arm: Reorganize PMCCNTR accesses, Aaron Lindsay, 2018/10/15