* Daniel P. Berrangé (berra...@redhat.com) wrote:
> The QEMUFile 'save_hook' callback has a 'size_t size' parameter.
>
> The RDMA impl of this has logic that takes different actions
> depending on whether the value is zero or non-zero. It has
> commented out logic that would have taken further actions
> if the value was negative.
>
> The only place where the 'save_hook' callback is invoked is
> the ram_control_save_page() method, which passes 'size'
> through from its caller. The only caller of this method is
> in turn control_save_page(). This method unconditionally
> passes the 'TARGET_PAGE_SIZE' constant for the 'size' parameter.
>
> IOW, the only scenario for 'size' that can execute in the
> qemu_rdma_save_page method is 'size > 0'. The remaining code
> has been unreachable since RDMA support was first introduced
> 9 years ago.
>
> Signed-off-by: Daniel P. Berrangé <berra...@redhat.com>
Ah good; less rdma code!
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> migration/rdma.c | 120 +++++++++--------------------------------------
> 1 file changed, 21 insertions(+), 99 deletions(-)
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 672d1958a9..6e7756bee7 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -1486,34 +1486,6 @@ static uint64_t qemu_rdma_make_wrid(uint64_t wr_id,
> uint64_t index,
> return result;
> }
>
> -/*
> - * Set bit for unregistration in the next iteration.
> - * We cannot transmit right here, but will unpin later.
> - */
> -static void qemu_rdma_signal_unregister(RDMAContext *rdma, uint64_t index,
> - uint64_t chunk, uint64_t wr_id)
> -{
> - if (rdma->unregistrations[rdma->unregister_next] != 0) {
> - error_report("rdma migration: queue is full");
> - } else {
> - RDMALocalBlock *block = &(rdma->local_ram_blocks.block[index]);
> -
> - if (!test_and_set_bit(chunk, block->unregister_bitmap)) {
> - trace_qemu_rdma_signal_unregister_append(chunk,
> - rdma->unregister_next);
> -
> - rdma->unregistrations[rdma->unregister_next++] =
> - qemu_rdma_make_wrid(wr_id, index, chunk);
> -
> - if (rdma->unregister_next == RDMA_SIGNALED_SEND_MAX) {
> - rdma->unregister_next = 0;
> - }
> - } else {
> - trace_qemu_rdma_signal_unregister_already(chunk);
> - }
> - }
> -}
> -
> /*
> * Consult the connection manager to see a work request
> * (of any kind) has completed.
> @@ -3278,23 +3250,7 @@ qio_channel_rdma_shutdown(QIOChannel *ioc,
> * Offset is an offset to be added to block_offset and used
> * to also lookup the corresponding RAMBlock.
> *
> - * @size > 0 :
> - * Initiate an transfer this size.
> - *
> - * @size == 0 :
> - * A 'hint' or 'advice' that means that we wish to speculatively
> - * and asynchronously unregister this memory. In this case, there is
> no
> - * guarantee that the unregister will actually happen, for example,
> - * if the memory is being actively transmitted. Additionally, the
> memory
> - * may be re-registered at any future time if a write within the same
> - * chunk was requested again, even if you attempted to unregister it
> - * here.
> - *
> - * @size < 0 : TODO, not yet supported
> - * Unregister the memory NOW. This means that the caller does not
> - * expect there to be any future RDMA transfers and we just want to
> clean
> - * things up. This is used in case the upper layer owns the memory and
> - * cannot wait for qemu_fclose() to occur.
> + * @size : Number of bytes to transfer
> *
> * @bytes_sent : User-specificed pointer to indicate how many bytes were
> * sent. Usually, this will not be more than a few bytes of
> @@ -3323,61 +3279,27 @@ static size_t qemu_rdma_save_page(QEMUFile *f, void
> *opaque,
>
> qemu_fflush(f);
>
> - if (size > 0) {
> - /*
> - * Add this page to the current 'chunk'. If the chunk
> - * is full, or the page doesn't belong to the current chunk,
> - * an actual RDMA write will occur and a new chunk will be formed.
> - */
> - ret = qemu_rdma_write(f, rdma, block_offset, offset, size);
> - if (ret < 0) {
> - error_report("rdma migration: write error! %d", ret);
> - goto err;
> - }
> -
> - /*
> - * We always return 1 bytes because the RDMA
> - * protocol is completely asynchronous. We do not yet know
> - * whether an identified chunk is zero or not because we're
> - * waiting for other pages to potentially be merged with
> - * the current chunk. So, we have to call qemu_update_position()
> - * later on when the actual write occurs.
> - */
> - if (bytes_sent) {
> - *bytes_sent = 1;
> - }
> - } else {
> - uint64_t index, chunk;
> -
> - /* TODO: Change QEMUFileOps prototype to be signed: size_t => long
> - if (size < 0) {
> - ret = qemu_rdma_drain_cq(f, rdma);
> - if (ret < 0) {
> - fprintf(stderr, "rdma: failed to synchronously drain"
> - " completion queue before
> unregistration.\n");
> - goto err;
> - }
> - }
> - */
> -
> - ret = qemu_rdma_search_ram_block(rdma, block_offset,
> - offset, size, &index, &chunk);
> -
> - if (ret) {
> - error_report("ram block search failed");
> - goto err;
> - }
> -
> - qemu_rdma_signal_unregister(rdma, index, chunk, 0);
> + /*
> + * Add this page to the current 'chunk'. If the chunk
> + * is full, or the page doesn't belong to the current chunk,
> + * an actual RDMA write will occur and a new chunk will be formed.
> + */
> + ret = qemu_rdma_write(f, rdma, block_offset, offset, size);
> + if (ret < 0) {
> + error_report("rdma migration: write error! %d", ret);
> + goto err;
> + }
>
> - /*
> - * TODO: Synchronous, guaranteed unregistration (should not occur
> during
> - * fast-path). Otherwise, unregisters will process on the next call
> to
> - * qemu_rdma_drain_cq()
> - if (size < 0) {
> - qemu_rdma_unregister_waiting(rdma);
> - }
> - */
> + /*
> + * We always return 1 bytes because the RDMA
> + * protocol is completely asynchronous. We do not yet know
> + * whether an identified chunk is zero or not because we're
> + * waiting for other pages to potentially be merged with
> + * the current chunk. So, we have to call qemu_update_position()
> + * later on when the actual write occurs.
> + */
> + if (bytes_sent) {
> + *bytes_sent = 1;
> }
>
> /*
> --
> 2.36.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
