Re: [PATCH V5 00/19] Live update: cpr-exec

[Steven Sistare <steven.sistare@oracle.com>]

On 10/1/2025 3:07 PM, Steven Sistare wrote:
> On 10/1/2025 2:56 PM, Peter Xu wrote:
>> On Wed, Oct 01, 2025 at 08:33:52AM -0700, Steve Sistare wrote:
>>> This patch series adds the live migration cpr-exec mode.
>>>
>>> The new user-visible interfaces are:
>>>    * cpr-exec (MigMode migration parameter)
>>>    * cpr-exec-command (migration parameter)
>>>
>>> cpr-exec mode is similar in most respects to cpr-transfer mode, with the
>>> primary difference being that old QEMU directly exec's new QEMU.  The user
>>> specifies the command to exec new QEMU in the migration parameter
>>> cpr-exec-command.
>>
>> It turns out I was right where I replied to patch 5; this fails the Windows
>> build.
>>
>> Smallest fix is to wrap qemu_memfd_create() with a CONFIG_LINUX ifdef,
>> returning -1 to mfd otherwise.
> 
> That does not make sense.  It already does that, which is why I used it:
> 
> util/memfd.c
> 
> int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
>                        uint64_t hugetlbsize, unsigned int seals, Error **errp)
> {
>      ...
> #ifdef CONFIG_LINUX
>      ...
>      return mfd;
> #else
>      error_setg_errno(errp, ENOSYS, "failed to create memfd");
> #endif
>      return -1;
> }
> 
> Did the windows build fail due to a different error?
> 
>> A better one is we only include cpr*.c in meson.build if it's linux.
>> Personally I'm OK if we go with the smaller one as of now, however then it
>> would definitely be nice to have a follow up series to reach the better
>> solution, if that makes sense.
>>
>> Feel free to use "make docker-test-build@fedora-win64-cross" for verifying
>> the changes.  I hope it'll work for you, even if for me currently it didn't
>> work due to a gitlab.com dns resolution pulling dtc src, where I didn't dig
>> deeper yet..
>>
>> The other thing is, this series doesn't apply on master branch.  I didn't
>> feel confident to do it myself on the vfio change, please have a look on
>> both issues.
> Ugh, they renamed everything.  I will rebase and send V6.

Actually that was easy to resolve, not worth a V6?

In patch "vfio: cpr-exec mode", drop the change in container.c, and instead
add MIG_MODE_CPR_EXEC to container-legacy.c here:

         if (migrate_add_blocker_modes(&vbasedev->cpr.mdev_blocker, errp,
                                       MIG_MODE_CPR_TRANSFER, MIG_MODE_CPR_EXEC,
                                       -1) < 0) {

- Steve