On Mon, Aug 17, 2026 at 10:24 PM Peter Xu <[email protected]> wrote: > > The unregister code was there since the first commit RDMA migration was > merged, but it was never functioning. Remove the dead code. > > Since the two control messages are the last ones, we don't even need to > worry about compatibility of legacy RDMA control commands, we can directly > remove the messages too. > > As a side effect, this patch closes a report by removing the code > completely. > > Reported-by: Tristan (@TristanInSec) > Closes: https://gitlab.com/qemu-project/qemu/-/work_items/4003 > Signed-off-by: Peter Xu <[email protected]> Hi Peter, hi Yanfei,
The change looks fine, and I have also tested to ensure it doesn't break compatibility with older versions. As already discussed, removing this code could result in more MRs being used during migration; however, once the migration is complete, they will be unregistered, so there is no leak. Reviewed-by: Jinpu Wang <[email protected]> > --- > migration/rdma.c | 133 ----------------------------------------- > migration/trace-events | 7 --- > 2 files changed, 140 deletions(-) > > diff --git a/migration/rdma.c b/migration/rdma.c > index 62a509b236..eae4afd6df 100644 > --- a/migration/rdma.c > +++ b/migration/rdma.c > @@ -142,8 +142,6 @@ enum { > RDMA_CONTROL_REGISTER_REQUEST, /* dynamic page registration */ > RDMA_CONTROL_REGISTER_RESULT, /* key to use after registration */ > RDMA_CONTROL_REGISTER_FINISHED, /* current iteration finished */ > - RDMA_CONTROL_UNREGISTER_REQUEST, /* dynamic UN-registration */ > - RDMA_CONTROL_UNREGISTER_FINISHED, /* unpinning finished */ > RDMA_CONTROL_NUM, > }; > > @@ -232,8 +230,6 @@ static const char *control_desc(unsigned int rdma_control) > [RDMA_CONTROL_REGISTER_REQUEST] = "REGISTER REQUEST", > [RDMA_CONTROL_REGISTER_RESULT] = "REGISTER RESULT", > [RDMA_CONTROL_REGISTER_FINISHED] = "REGISTER FINISHED", > - [RDMA_CONTROL_UNREGISTER_REQUEST] = "UNREGISTER REQUEST", > - [RDMA_CONTROL_UNREGISTER_FINISHED] = "UNREGISTER FINISHED", > }; > > if (rdma_control >= RDMA_CONTROL_NUM) { > @@ -370,9 +366,6 @@ typedef struct RDMAContext { > int total_registrations; > int total_writes; > > - int unregister_current, unregister_next; > - uint64_t unregistrations[RDMA_SIGNALED_SEND_MAX]; > - > GHashTable *blockmap; > > /* the RDMAContext for return path */ > @@ -1186,91 +1179,6 @@ static int qemu_rdma_reg_control(RDMAContext *rdma, > int idx) > return -1; > } > > -/* > - * Perform a non-optimized memory unregistration after every transfer > - * for demonstration purposes, only if pin-all is not requested. > - * > - * Potential optimizations: > - * 1. Start a new thread to run this function continuously > - - for bit clearing > - - and for receipt of unregister messages > - * 2. Use an LRU. > - * 3. Use workload hints. > - */ > -static int qemu_rdma_unregister_waiting(RDMAContext *rdma) > -{ > - Error *err = NULL; > - > - while (rdma->unregistrations[rdma->unregister_current]) { > - int ret; > - uint64_t wr_id = rdma->unregistrations[rdma->unregister_current]; > - uint64_t chunk = > - (wr_id & RDMA_WRID_CHUNK_MASK) >> RDMA_WRID_CHUNK_SHIFT; > - uint64_t index = > - (wr_id & RDMA_WRID_BLOCK_MASK) >> RDMA_WRID_BLOCK_SHIFT; > - RDMALocalBlock *block = > - &(rdma->local_ram_blocks.block[index]); > - RDMARegister reg = { .current_index = index }; > - RDMAControlHeader resp = { .type = RDMA_CONTROL_UNREGISTER_FINISHED, > - }; > - RDMAControlHeader head = { .len = sizeof(RDMARegister), > - .type = RDMA_CONTROL_UNREGISTER_REQUEST, > - .repeat = 1, > - }; > - > - trace_qemu_rdma_unregister_waiting_proc(chunk, > - rdma->unregister_current); > - > - rdma->unregistrations[rdma->unregister_current] = 0; > - rdma->unregister_current++; > - > - if (rdma->unregister_current == RDMA_SIGNALED_SEND_MAX) { > - rdma->unregister_current = 0; > - } > - > - > - /* > - * Unregistration is speculative (because migration is > single-threaded > - * and we cannot break the protocol's inifinband message ordering). > - * Thus, if the memory is currently being used for transmission, > - * then abort the attempt to unregister and try again > - * later the next time a completion is received for this memory. > - */ > - clear_bit(chunk, block->unregister_bitmap); > - > - if (test_bit(chunk, block->transit_bitmap)) { > - trace_qemu_rdma_unregister_waiting_inflight(chunk); > - continue; > - } > - > - trace_qemu_rdma_unregister_waiting_send(chunk); > - > - ret = ibv_dereg_mr(block->pmr[chunk]); > - block->pmr[chunk] = NULL; > - block->remote_keys[chunk] = 0; > - > - if (ret != 0) { > - error_report("unregistration chunk failed: %s", > - strerror(ret)); > - return -1; > - } > - rdma->total_registrations--; > - > - reg.key.chunk = chunk; > - register_to_network(rdma, ®); > - ret = qemu_rdma_exchange_send(rdma, &head, (uint8_t *) ®, > - &resp, NULL, NULL, &err); > - if (ret < 0) { > - error_report_err(err); > - return -1; > - } > - > - trace_qemu_rdma_unregister_waiting_complete(chunk); > - } > - > - return 0; > -} > - > static uint64_t qemu_rdma_make_wrid(uint64_t wr_id, uint64_t index, > uint64_t chunk) > { > @@ -2757,8 +2665,6 @@ static int qemu_rdma_drain_cq(RDMAContext *rdma) > } > } > > - qemu_rdma_unregister_waiting(rdma); > - > return 0; > } > > @@ -3336,10 +3242,6 @@ int rdma_registration_handle(QEMUFile *f) > .type = RDMA_CONTROL_REGISTER_RESULT, > .repeat = 0, > }; > - RDMAControlHeader unreg_resp = { .len = 0, > - .type = RDMA_CONTROL_UNREGISTER_FINISHED, > - .repeat = 0, > - }; > RDMAControlHeader blocks = { .type = RDMA_CONTROL_RAM_BLOCKS_RESULT, > .repeat = 1 }; > QIOChannelRDMA *rioc; > @@ -3552,41 +3454,6 @@ int rdma_registration_handle(QEMUFile *f) > ret = qemu_rdma_post_send_control(rdma, > (uint8_t *) results, ®_resp, &err); > > - if (ret < 0) { > - error_report_err(err); > - goto err; > - } > - break; > - case RDMA_CONTROL_UNREGISTER_REQUEST: > - trace_rdma_registration_handle_unregister(head.repeat); > - unreg_resp.repeat = head.repeat; > - registers = (RDMARegister *) rdma->wr_data[idx].control_curr; > - > - for (int count = 0; count < head.repeat; count++) { > - reg = ®isters[count]; > - network_to_register(reg); > - > - trace_rdma_registration_handle_unregister_loop(count, > - reg->current_index, reg->key.chunk); > - > - block = &(rdma->local_ram_blocks.block[reg->current_index]); > - > - ret = ibv_dereg_mr(block->pmr[reg->key.chunk]); > - block->pmr[reg->key.chunk] = NULL; > - > - if (ret != 0) { > - error_report("rdma unregistration chunk failed: %s", > - strerror(errno)); > - goto err; > - } > - > - rdma->total_registrations--; > - > - > trace_rdma_registration_handle_unregister_success(reg->key.chunk); > - } > - > - ret = qemu_rdma_post_send_control(rdma, NULL, &unreg_resp, &err); > - > if (ret < 0) { > error_report_err(err); > goto err; > diff --git a/migration/trace-events b/migration/trace-events > index af0e784535..d1fe8f1382 100644 > --- a/migration/trace-events > +++ b/migration/trace-events > @@ -244,10 +244,6 @@ qemu_rdma_advise_mr(const char *name, uint32_t len, > uint64_t addr, const char *r > qemu_rdma_resolve_host_trying(const char *host, const char *ip) "Trying %s > => %s" > qemu_rdma_signal_unregister_append(uint64_t chunk, int pos) "Appending > unregister chunk %" PRIu64 " at position %d" > qemu_rdma_signal_unregister_already(uint64_t chunk) "Unregister chunk %" > PRIu64 " already in queue" > -qemu_rdma_unregister_waiting_inflight(uint64_t chunk) "Cannot unregister > inflight chunk: %" PRIu64 > -qemu_rdma_unregister_waiting_proc(uint64_t chunk, int pos) "Processing > unregister for chunk: %" PRIu64 " at position %d" > -qemu_rdma_unregister_waiting_send(uint64_t chunk) "Sending unregister for > chunk: %" PRIu64 > -qemu_rdma_unregister_waiting_complete(uint64_t chunk) "Unregister for chunk: > %" PRIu64 " complete." > qemu_rdma_write_flush(int sent) "sent total: %d" > qemu_rdma_write_one_block(int count, int block, uint64_t chunk, uint64_t > current, uint64_t len, int nb_sent, int nb_chunks) "(%d) Not clobbering: > block: %d chunk %" PRIu64 " current %" PRIu64 " len %" PRIu64 " %d %d" > qemu_rdma_write_one_post(uint64_t chunk, long addr, long remote, uint32_t > len) "Posting chunk: %" PRIu64 ", addr: 0x%lx remote: 0x%lx, bytes %" PRIu32 > @@ -266,9 +262,6 @@ rdma_registration_handle_ram_blocks_loop(const char > *name, uint64_t offset, uint > rdma_registration_handle_register(int requests) "%d requests" > rdma_registration_handle_register_loop(int req, int index, uint64_t addr, > uint64_t chunks) "Registration request (%d): index %d, current_addr %" PRIu64 > " chunks: %" PRIu64 > rdma_registration_handle_register_rkey(int rkey) "0x%x" > -rdma_registration_handle_unregister(int requests) "%d requests" > -rdma_registration_handle_unregister_loop(int count, int index, uint64_t > chunk) "Unregistration request (%d): index %d, chunk %" PRIu64 > -rdma_registration_handle_unregister_success(uint64_t chunk) "%" PRIu64 > rdma_registration_handle_wait(void) "" > rdma_registration_start(uint64_t flags) "%" PRIu64 > rdma_registration_stop(uint64_t flags) "%" PRIu64 > -- > 2.54.0 >
