Re: [Qemu-devel] [PATCH 5/5] migration: disable RDMA WRITR after postcopy started.

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* 858585 jemmy (jemmy858585@gmail.com) wrote:
> On Wed, Apr 11, 2018 at 11:56 PM, Dr. David Alan Gilbert
> <dgilbert@redhat.com> wrote:
> > * Lidong Chen (jemmy858585@gmail.com) wrote:
> >> RDMA write operations are performed with no notification to the destination
> >> qemu, then the destination qemu can not wakeup. So disable RDMA WRITE after
> >> postcopy started.
> >>
> >> Signed-off-by: Lidong Chen <lidongchen@tencent.com>
> >
> > This patch needs to be near the beginning of the series; at the moment a
> > bisect would lead you to the middle of the series which had return
> > paths, but then would fail to work properly because it would try and use
> > the RDMA code.
> 
> I will fix this problem in next version.
> 
> >
> >> ---
> >>  migration/qemu-file.c |  3 ++-
> >>  migration/rdma.c      | 12 ++++++++++++
> >>  2 files changed, 14 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> >> index 8acb574..a64ac3a 100644
> >> --- a/migration/qemu-file.c
> >> +++ b/migration/qemu-file.c
> >> @@ -260,7 +260,8 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
> >>          int ret = f->hooks->save_page(f, f->opaque, block_offset,
> >>                                        offset, size, bytes_sent);
> >>          f->bytes_xfer += size;
> >> -        if (ret != RAM_SAVE_CONTROL_DELAYED) {
> >> +        if (ret != RAM_SAVE_CONTROL_DELAYED &&
> >> +            ret != RAM_SAVE_CONTROL_NOT_SUPP) {
> >
> > What about f->bytes_xfer in this case?
> 
> f->bytes_xfer should not update when RAM_SAVE_CONTROL_NOT_SUPP.
> I will fix this problem in next version.
> 
> >
> > Is there anything we have to do at the switchover into postcopy to make
> > sure that all pages have been received?
> 
> ram_save_iterate invoke ram_control_after_iterate(f, RAM_CONTROL_ROUND),
> so before next iteration which switchover into postcopy, all the pages
> sent by previous
> iteration have been received.

OK, great.

Dave

> >
> > Dave
> >
> >>              if (bytes_sent && *bytes_sent > 0) {
> >>                  qemu_update_position(f, *bytes_sent);
> >>              } else if (ret < 0) {
> >> diff --git a/migration/rdma.c b/migration/rdma.c
> >> index 81be482..8529ddd 100644
> >> --- a/migration/rdma.c
> >> +++ b/migration/rdma.c
> >> @@ -2964,6 +2964,10 @@ static size_t qemu_rdma_save_page(QEMUFile *f, void *opaque,
> >>
> >>      CHECK_ERROR_STATE();
> >>
> >> +    if (migrate_get_current()->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> >> +        return RAM_SAVE_CONTROL_NOT_SUPP;
> >> +    }
> >> +
> >>      qemu_fflush(f);
> >>
> >>      if (size > 0) {
> >> @@ -3528,6 +3532,10 @@ static int qemu_rdma_registration_start(QEMUFile *f, void *opaque,
> >>
> >>      CHECK_ERROR_STATE();
> >>
> >> +    if (migrate_get_current()->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> >> +        return 0;
> >> +    }
> >> +
> >>      trace_qemu_rdma_registration_start(flags);
> >>      qemu_put_be64(f, RAM_SAVE_FLAG_HOOK);
> >>      qemu_fflush(f);
> >> @@ -3550,6 +3558,10 @@ static int qemu_rdma_registration_stop(QEMUFile *f, void *opaque,
> >>
> >>      CHECK_ERROR_STATE();
> >>
> >> +    if (migrate_get_current()->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> >> +        return 0;
> >> +    }
> >> +
> >>      qemu_fflush(f);
> >>      ret = qemu_rdma_drain_cq(f, rdma);
> >>
> >> --
> >> 1.8.3.1
> >>
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK