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Re: [Qemu-devel] [PATCH v5 18/45] MIG_CMD_PACKAGED: Send a packaged chun
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH v5 18/45] MIG_CMD_PACKAGED: Send a packaged chunk of migration stream |
Date: |
Fri, 13 Mar 2015 11:55:58 +1100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Wed, Feb 25, 2015 at 04:51:41PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> MIG_CMD_PACKAGED is a migration command that allows a chunk
> of migration stream to be sent in one go, and be received by
> a separate instance of the loadvm loop while not interacting
> with the migration stream.
Hrm. I'd be more comfortable if the semantics of CMD_PACKAGED were
defined in terms of visible effects on the other end, rather than in
terms of how it's implemented internally.
> This is used by postcopy to load device state (from the package)
> while loading memory pages from the main stream.
Which makes the above paragraph a bit misleading - the whole point
here is that loading the package data *does* interact with the
migration stream - just that it's the migration stream after the end
of the package.
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
> include/sysemu/sysemu.h | 4 +++
> savevm.c | 82
> +++++++++++++++++++++++++++++++++++++++++++++++++
> trace-events | 4 +++
> 3 files changed, 90 insertions(+)
>
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index d6a6d51..e83bf80 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -87,6 +87,7 @@ enum qemu_vm_cmd {
> MIG_CMD_INVALID = 0, /* Must be 0 */
> MIG_CMD_OPEN_RETURN_PATH, /* Tell the dest to open the Return path */
> MIG_CMD_PING, /* Request a PONG on the RP */
> + MIG_CMD_PACKAGED, /* Send a wrapped stream within this stream */
>
> MIG_CMD_POSTCOPY_ADVISE = 20, /* Prior to any page transfers, just
> warn we might want to do PC */
> @@ -101,6 +102,8 @@ enum qemu_vm_cmd {
>
> };
>
> +#define MAX_VM_CMD_PACKAGED_SIZE (1ul << 24)
> +
> bool qemu_savevm_state_blocked(Error **errp);
> void qemu_savevm_state_begin(QEMUFile *f,
> const MigrationParams *params);
> @@ -113,6 +116,7 @@ void qemu_savevm_command_send(QEMUFile *f, enum
> qemu_vm_cmd command,
> uint16_t len, uint8_t *data);
> void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
> void qemu_savevm_send_open_return_path(QEMUFile *f);
> +void qemu_savevm_send_packaged(QEMUFile *f, const QEMUSizedBuffer *qsb);
> void qemu_savevm_send_postcopy_advise(QEMUFile *f);
> void qemu_savevm_send_postcopy_listen(QEMUFile *f);
> void qemu_savevm_send_postcopy_run(QEMUFile *f);
> diff --git a/savevm.c b/savevm.c
> index e31ccb0..f65bff3 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -636,6 +636,38 @@ void qemu_savevm_send_open_return_path(QEMUFile *f)
> qemu_savevm_command_send(f, MIG_CMD_OPEN_RETURN_PATH, 0, NULL);
> }
>
> +/* We have a buffer of data to send; we don't want that all to be loaded
> + * by the command itself, so the command contains just the length of the
> + * extra buffer that we then send straight after it.
> + * TODO: Must be a better way to organise that
> + */
> +void qemu_savevm_send_packaged(QEMUFile *f, const QEMUSizedBuffer *qsb)
> +{
> + size_t cur_iov;
> + size_t len = qsb_get_length(qsb);
> + uint32_t tmp;
> +
> + tmp = cpu_to_be32(len);
> +
> + trace_qemu_savevm_send_packaged();
> + qemu_savevm_command_send(f, MIG_CMD_PACKAGED, 4, (uint8_t *)&tmp);
> +
> + /* all the data follows (concatinating the iov's) */
> + for (cur_iov = 0; cur_iov < qsb->n_iov; cur_iov++) {
> + /* The iov entries are partially filled */
> + size_t towrite = (qsb->iov[cur_iov].iov_len > len) ?
> + len :
> + qsb->iov[cur_iov].iov_len;
> + len -= towrite;
> +
> + if (!towrite) {
> + break;
> + }
> +
> + qemu_put_buffer(f, qsb->iov[cur_iov].iov_base, towrite);
> + }
> +}
> +
> /* Send prior to any postcopy transfer */
> void qemu_savevm_send_postcopy_advise(QEMUFile *f)
> {
> @@ -1265,6 +1297,48 @@ static int
> loadvm_process_command_simple_lencheck(const char *name,
> return 0;
> }
>
> +/* Immediately following this command is a blob of data containing an
> embedded
> + * chunk of migration stream; read it and load it.
> + */
> +static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis,
> + uint32_t length)
> +{
> + int ret;
> + uint8_t *buffer;
> + QEMUSizedBuffer *qsb;
> +
> + trace_loadvm_handle_cmd_packaged(length);
> +
> + if (length > MAX_VM_CMD_PACKAGED_SIZE) {
> + error_report("Unreasonably large packaged state: %u", length);
> + return -1;
It would be a good idea to check this on the send side as well as
receive, wouldn't it?
> + }
> + buffer = g_malloc0(length);
> + ret = qemu_get_buffer(mis->file, buffer, (int)length);
> + if (ret != length) {
> + g_free(buffer);
> + error_report("CMD_PACKAGED: Buffer receive fail ret=%d length=%d\n",
> + ret, length);
> + return (re/t < 0) ? ret : -EAGAIN;
> + }
> + trace_loadvm_handle_cmd_packaged_received(ret);
> +
> + /* Setup a dummy QEMUFile that actually reads from the buffer */
> + qsb = qsb_create(buffer, length);
> + g_free(buffer); /* Because qsb_create copies */
> + if (!qsb) {
> + error_report("Unable to create qsb");
> + }
> + QEMUFile *packf = qemu_bufopen("r", qsb);
> +
> + ret = qemu_loadvm_state_main(packf, mis);
> + trace_loadvm_handle_cmd_packaged_main(ret);
> + qemu_fclose(packf);
> + qsb_free(qsb);
> +
> + return ret;
> +}
> +
> /*
> * Process an incoming 'QEMU_VM_COMMAND'
> * negative return on error (will issue error message)
> @@ -1315,6 +1389,14 @@ static int loadvm_process_command(QEMUFile *f)
> migrate_send_rp_pong(mis, tmp32);
> break;
>
> + case MIG_CMD_PACKAGED:
> + if (loadvm_process_command_simple_lencheck("CMD_POSTCOPY_PACKAGED",
> + len, 4)) {
> + return -1;
> + }
> + tmp32 = qemu_get_be32(f);
> + return loadvm_handle_cmd_packaged(mis, tmp32);
> +
> case MIG_CMD_POSTCOPY_ADVISE:
> if (loadvm_process_command_simple_lencheck("CMD_POSTCOPY_ADVISE",
> len, 16)) {
> diff --git a/trace-events b/trace-events
> index 050f553..cbf995c 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1171,6 +1171,10 @@ qemu_loadvm_state_main(void) ""
> qemu_loadvm_state_main_quit_parent(void) ""
> qemu_loadvm_state_post_main(int ret) "%d"
> qemu_loadvm_state_section_startfull(uint32_t section_id, const char *idstr,
> uint32_t instance_id, uint32_t version_id) "%u(%s) %u %u"
> +qemu_savevm_send_packaged(void) ""
> +loadvm_handle_cmd_packaged(unsigned int length) "%u"
> +loadvm_handle_cmd_packaged_main(int ret) "%d"
> +loadvm_handle_cmd_packaged_received(int ret) "%d"
> loadvm_postcopy_handle_advise(void) ""
> loadvm_postcopy_handle_end(void) ""
> loadvm_postcopy_handle_listen(void) ""
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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