On Thu, Oct 24, 2024 at 05:30:48PM -0400, Peter Xu wrote:
> Based-on: <20241024165627.1372621-1-peterx@redhat.com>
> CI: https://gitlab.com/peterx/qemu/-/pipelines/1511349805
>
> This is a follow up of below patch from Avihai as a replacement:
>
> https://lore.kernel.org/qemu-devel/20241020130108.27148-3-avihaih@nvidia.com/
>
> This is v3 of the series, and it happened again: changelog doesn't make
> sense to compare to v2 because it's rewritten. Meanwhile, now this series
> is based on the other TYPE_SINGLETON series I posted just now:
>
> https://lore.kernel.org/r/20241024165627.1372621-1-peterx@redhat.com
>
> It turns out I found more things to cleanup, as the versions spin up.
>
> Patch 1: I found that object_ref() in migration thread is actually also
> racy.. this should fix it.
>
> Patch 2-7: It turns out I decided to clean things up first, then it'll
> make my last patch easier on adding the mutex protection for
> the current_migration reference
>
> Patch 8: The fix for NULL-dereference / race for the exported
> functions. VFIO can hit it only because VFIO's specialty
> in using migration helpers in vmstate handlers, I guess. I
> found most functions always safe because even if they're used
> outside migration/ they're most likely still invoked with
> migration thread context. So I found only two functions that
> really need protections, exactly what VFIO is using.
I queued patch 1-5.
Ideally 6+7 can be a single patch, then we don't need to move DEVICE into
migration_is_active() at all. Also that might break VFIO as Avihai pointed
out on VGA sync. Avihai, I'd still appreciate if you could consider look
at vfio to behave like what kvm/vhost/.. is doing, by accepting log_sync()
before log_start().
Patch 8 still rely on singleton series, which will become rfc to be
reposted, so probably no rush on that.
>
> Comments welcomed, thanks.
>
> Peter Xu (8):
> migration: Take migration object refcount earlier for threads
> migration: Unexport dirty_bitmap_mig_init()
> migration: Unexport ram_mig_init()
> migration: Drop migration_is_setup_or_active()
> migration: Drop migration_is_idle()
> migration: Drop migration_is_device()
> migration: Unexport migration_is_active()
> migration: Protect updates to current_migration with a mutex
>
> include/migration/misc.h | 11 +---
> migration/migration.h | 8 +++
> migration/ram.h | 1 +
> hw/vfio/common.c | 6 +-
> hw/virtio/virtio-mem.c | 2 +-
> migration/migration.c | 118 +++++++++++++++++++--------------------
> migration/ram.c | 7 +--
> net/vhost-vdpa.c | 3 +-
> system/dirtylimit.c | 3 +-
> system/qdev-monitor.c | 4 +-
> 10 files changed, 81 insertions(+), 82 deletions(-)
>
> --
> 2.45.0
>
--
Peter Xu