From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51676) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZK8on-0005zq-UJ for qemu-devel@nongnu.org; Tue, 28 Jul 2015 13:37:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZK8oi-00015x-Cf for qemu-devel@nongnu.org; Tue, 28 Jul 2015 13:37:33 -0400 Received: from mail-qk0-x22c.google.com ([2607:f8b0:400d:c09::22c]:34498) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZK8oi-00015s-9l for qemu-devel@nongnu.org; Tue, 28 Jul 2015 13:37:28 -0400 Received: by qkfc129 with SMTP id c129so54095587qkf.1 for ; Tue, 28 Jul 2015 10:37:28 -0700 (PDT) Sender: =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Tue, 28 Jul 2015 19:36:43 +0200 Message-Id: <1438105003-29501-10-git-send-email-marcandre.lureau@redhat.com> In-Reply-To: <1438105003-29501-1-git-send-email-marcandre.lureau@redhat.com> References: <1438105003-29501-1-git-send-email-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH v2 9/9] vhost-user: document migration log List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: haifeng.lin@huawei.com, mst@redhat.com, thibaut.collet@6wind.com, jasowang@redhat.com, pbonzini@redhat.com, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Signed-off-by: Marc-André Lureau --- docs/specs/vhost-user.txt | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt index 0062baa..2cf9ab4 100644 --- a/docs/specs/vhost-user.txt +++ b/docs/specs/vhost-user.txt @@ -120,6 +120,7 @@ There are several messages that the master sends with file descriptors passed in the ancillary data: * VHOST_SET_MEM_TABLE + * VHOST_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD) * VHOST_SET_LOG_FD * VHOST_SET_VRING_KICK * VHOST_SET_VRING_CALL @@ -135,6 +136,11 @@ As older slaves don't support negotiating protocol features, a feature bit was dedicated for this purpose: #define VHOST_USER_F_PROTOCOL_FEATURES 30 +Protocol features +----------------- + +#define VHOST_USER_PROTOCOL_F_LOG_SHMFD 0 + Message types ------------- @@ -301,3 +307,39 @@ Message types Bits (0-7) of the payload contain the vring index. Bit 8 is the invalid FD flag. This flag is set when there is no file descriptor in the ancillary data. + +Migration +--------- + +During live migration, the master may need to track the modifications +the slave makes to the memory mapped regions. The client should mark +the dirty pages in a log. Once it complies to this logging, it may +declare VHOST_F_LOG_ALL has a vhost feature. + +All the modifications to memory pointed by vring "descriptor" should +be marked. Modifications to "used" vring should be marked if +VHOST_VRING_F_LOG is part of ring's features. + +Dirty pages are of size: +#define VHOST_LOG_PAGE 0x1000 + +The log memory fd is provided in the ancillary data of +VHOST_USER_SET_LOG_BASE message when the slave has +VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol feature. + +The size of the log may be computed by using all the known guest +addresses. The log covers from address 0 to the maximum of guest +regions. In pseudo-code, to mark page at "addr" as dirty: + +page = addr / VHOST_LOG_PAGE +log[page / 8] |= 1 << page % 8 + +Use atomic operations, as the log may be concurrently manipulated. + +VHOST_USER_SET_LOG_FD is an optional message with an eventfd in +ancillary data, it may be used to inform the master that the log has +been modified. + +Once the source has finished migration, VHOST_USER_RESET_OWNER message +will be sent by the source. No further update must be done before the +destination takes over with new regions & rings. -- 2.4.3