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

[858585 jemmy]

On Wed, Apr 11, 2018 at 11:56 PM, Dr. David Alan Gilbert
<address@hidden> wrote:
> * Lidong Chen (address@hidden) 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 <address@hidden>
>
> 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.

>
> 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 / address@hidden / Manchester, UK