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Re: [PATCH] migration/rdma: Fix return-path case
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH] migration/rdma: Fix return-path case |
Date: |
Tue, 14 Mar 2023 18:03:34 +0000 |
User-agent: |
Mutt/2.2.9 (2022-11-12) |
* Peter Xu (peterx@redhat.com) wrote:
> On Tue, Mar 14, 2023 at 05:15:58PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > The RDMA code has return-path handling code, but it's only enabled
> > if postcopy is enabled; if the 'return-path' migration capability
> > is enabled, the return path is NOT setup but the core migration
> > code still tries to use it and breaks.
> >
> > Enable the RDMA return path if either postcopy or the return-path
> > capability is enabled.
> >
> > bz: https://bugzilla.redhat.com/show_bug.cgi?id=2063615
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
> Acked-by: Peter Xu <peterx@redhat.com>
>
> > @@ -3373,7 +3373,8 @@ static int qemu_rdma_accept(RDMAContext *rdma)
> > * initialize the RDMAContext for return path for postcopy after first
> > * connection request reached.
> > */
> > - if (migrate_postcopy() && !rdma->is_return_path) {
> > + if ((migrate_postcopy() || migrate_use_return_path())
> > + && !rdma->is_return_path) {
> > rdma_return_path = qemu_rdma_data_init(rdma->host_port, NULL);
> > if (rdma_return_path == NULL) {
> > rdma_ack_cm_event(cm_event);
>
> It's not extremely clear to me yet on when we should use migrate_postcopy()
> and when to use migrate_postcopy_ram(). I think it's because I don't know
> enough on the dirty-bitmaps capability. Do we have some good documentation
> somewhere?
Hmm that's probably a good point.
> Not much I get from the qapi doc..
>
> # @dirty-bitmaps: If enabled, QEMU will migrate named dirty bitmaps.
> # (since 2.12)
I don't know of any good docs; I think this is a blocks mechanism; I'm
not even sure if it needs the return path.
Dave
> Thanks,
>
> --
> Peter Xu
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK