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bh=/vTIKeW8XrgwF9pMNPBG3wnVd2MZ26Y8J8CG+dWGEUE=; b=gmf8YIi6cPEX0Ku3YYcGOGbCdRxy9//AiC70ygp93Loj+HNbtil36JBLna0HlzB9mZ7CuP ODeui5C3rmre01asVAZt3NrUyODNf5IcNYYVARWrB/Nz7FUVws6aHiZcMwI/fd3n/40L2O 5rKIic/LyPPBTj4h08VGA6rlX3Q/XAI= X-MC-Unique: odpFE8nlP1SH1vWkJQQ6jw-1 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , "Dr. David Alan Gilbert" , qemu-block@nongnu.org, Stefan Hajnoczi , Hailiang Zhang , Juan Quintela , Fam Zheng Subject: [PATCH 03/20] migration: remove unreachble RDMA code in save_hook impl Date: Tue, 24 May 2022 12:02:18 +0100 Message-Id: <20220524110235.145079-4-berrange@redhat.com> In-Reply-To: <20220524110235.145079-1-berrange@redhat.com> References: <20220524110235.145079-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer2=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer2=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1653390762147100001 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. Berrang=C3=A9 Reviewed-by: Dr. David Alan Gilbert Reviewed-by: Eric Blake --- 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; } =20 -/* - * 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] !=3D 0) { - error_report("rdma migration: queue is full"); - } else { - RDMALocalBlock *block =3D &(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++] =3D - qemu_rdma_make_wrid(wr_id, index, chunk); - - if (rdma->unregister_next =3D=3D RDMA_SIGNALED_SEND_MAX) { - rdma->unregister_next =3D 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 =3D=3D 0 : - * A 'hint' or 'advice' that means that we wish to speculatively - * and asynchronously unregister this memory. In this case, there i= s no - * guarantee that the unregister will actually happen, for example, - * if the memory is being actively transmitted. Additionally, the m= emory - * may be re-registered at any future time if a write within the sa= me - * 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, =20 qemu_fflush(f); =20 - 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 =3D 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 =3D 1; - } - } else { - uint64_t index, chunk; - - /* TODO: Change QEMUFileOps prototype to be signed: size_t =3D> lo= ng - if (size < 0) { - ret =3D qemu_rdma_drain_cq(f, rdma); - if (ret < 0) { - fprintf(stderr, "rdma: failed to synchronously drain" - " completion queue before unregistration.\= n"); - goto err; - } - } - */ - - ret =3D 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 =3D qemu_rdma_write(f, rdma, block_offset, offset, size); + if (ret < 0) { + error_report("rdma migration: write error! %d", ret); + goto err; + } =20 - /* - * TODO: Synchronous, guaranteed unregistration (should not occur = during - * fast-path). Otherwise, unregisters will process on the next cal= l 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 =3D 1; } =20 /* --=20 2.36.1