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Re: [Qemu-devel] [PATCH v5 11/45] Return path: Send responses from desti
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH v5 11/45] Return path: Send responses from destination to source |
Date: |
Wed, 11 Mar 2015 12:54:42 +1100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Tue, Mar 10, 2015 at 02:34:03PM +0000, Dr. David Alan Gilbert wrote:
> * David Gibson (address@hidden) wrote:
> > On Wed, Feb 25, 2015 at 04:51:34PM +0000, Dr. David Alan Gilbert (git)
> > wrote:
> > > From: "Dr. David Alan Gilbert" <address@hidden>
> > >
> > > Add migrate_send_rp_message to send a message from destination to source
> > > along the return path.
> > > (It uses a mutex to let it be called from multiple threads)
> > > Add migrate_send_rp_shut to send a 'shut' message to indicate
> > > the destination is finished with the RP.
> > > Add migrate_send_rp_ack to send a 'PONG' message in response to a PING
> > > Use it in the CMD_PING handler
> > >
> > > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > > ---
> > > include/migration/migration.h | 17 ++++++++++++++++
> > > migration/migration.c | 45
> > > +++++++++++++++++++++++++++++++++++++++++++
> > > savevm.c | 2 +-
> > > trace-events | 1 +
> > > 4 files changed, 64 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/migration/migration.h b/include/migration/migration.h
> > > index c514dd4..6775747 100644
> > > --- a/include/migration/migration.h
> > > +++ b/include/migration/migration.h
> > > @@ -41,6 +41,13 @@ struct MigrationParams {
> > > bool shared;
> > > };
> > >
> > > +/* Commands sent on the return path from destination to source*/
> > > +enum mig_rpcomm_cmd {
> >
> > "command" doesn't seem like quite the right description for these rp
> > messages.
>
> Would you prefer 'message' ?
Perhaps "message type" to distinguish from the the blob including both
tag and data.
> > > + MIG_RP_CMD_INVALID = 0, /* Must be 0 */
> > > + MIG_RP_CMD_SHUT, /* sibling will not send any more RP
> > > messages */
> > > + MIG_RP_CMD_PONG, /* Response to a PING; data (seq: be32 ) */
> > > +};
> > > +
> > > typedef struct MigrationState MigrationState;
> > >
> > > /* State for the incoming migration */
> > > @@ -48,6 +55,7 @@ struct MigrationIncomingState {
> > > QEMUFile *file;
> > >
> > > QEMUFile *return_path;
> > > + QemuMutex rp_mutex; /* We send replies from multiple threads
> > > */
> > > };
> > >
> > > MigrationIncomingState *migration_incoming_get_current(void);
> > > @@ -169,6 +177,15 @@ int64_t migrate_xbzrle_cache_size(void);
> > >
> > > int64_t xbzrle_cache_resize(int64_t new_size);
> > >
> > > +/* Sending on the return path - generic and then for each message type */
> > > +void migrate_send_rp_message(MigrationIncomingState *mis,
> > > + enum mig_rpcomm_cmd cmd,
> > > + uint16_t len, uint8_t *data);
> > > +void migrate_send_rp_shut(MigrationIncomingState *mis,
> > > + uint32_t value);
> > > +void migrate_send_rp_pong(MigrationIncomingState *mis,
> > > + uint32_t value);
> > > +
> > > void ram_control_before_iterate(QEMUFile *f, uint64_t flags);
> > > void ram_control_after_iterate(QEMUFile *f, uint64_t flags);
> > > void ram_control_load_hook(QEMUFile *f, uint64_t flags);
> > > diff --git a/migration/migration.c b/migration/migration.c
> > > index a36ea65..80d234c 100644
> > > --- a/migration/migration.c
> > > +++ b/migration/migration.c
> > > @@ -78,6 +78,7 @@ MigrationIncomingState
> > > *migration_incoming_state_new(QEMUFile* f)
> > > {
> > > mis_current = g_malloc0(sizeof(MigrationIncomingState));
> > > mis_current->file = f;
> > > + qemu_mutex_init(&mis_current->rp_mutex);
> > >
> > > return mis_current;
> > > }
> > > @@ -88,6 +89,50 @@ void migration_incoming_state_destroy(void)
> > > mis_current = NULL;
> > > }
> > >
> > > +/*
> > > + * Send a message on the return channel back to the source
> > > + * of the migration.
> > > + */
> > > +void migrate_send_rp_message(MigrationIncomingState *mis,
> > > + enum mig_rpcomm_cmd cmd,
> > > + uint16_t len, uint8_t *data)
> >
> > Using (void *) for data would avoid casts in a bunch of the callers.
>
> Fixed; thanks.
>
> > > +{
> > > + trace_migrate_send_rp_message((int)cmd, len);
> > > + qemu_mutex_lock(&mis->rp_mutex);
> > > + qemu_put_be16(mis->return_path, (unsigned int)cmd);
> > > + qemu_put_be16(mis->return_path, len);
> > > + qemu_put_buffer(mis->return_path, data, len);
> > > + qemu_fflush(mis->return_path);
> > > + qemu_mutex_unlock(&mis->rp_mutex);
> > > +}
> > > +
> > > +/*
> > > + * Send a 'SHUT' message on the return channel with the given value
> > > + * to indicate that we've finished with the RP. None-0 value indicates
> > > + * error.
> > > + */
> > > +void migrate_send_rp_shut(MigrationIncomingState *mis,
> > > + uint32_t value)
> > > +{
> > > + uint32_t buf;
> > > +
> > > + buf = cpu_to_be32(value);
> > > + migrate_send_rp_message(mis, MIG_RP_CMD_SHUT, 4, (uint8_t *)&buf);
> >
> > ^ sizeof(buf)
> > would be safer
>
> Done.
>
> > > +}
> > > +
> > > +/*
> > > + * Send a 'PONG' message on the return channel with the given value
> > > + * (normally in response to a 'PING')
> > > + */
> > > +void migrate_send_rp_pong(MigrationIncomingState *mis,
> > > + uint32_t value)
> > > +{
> > > + uint32_t buf;
> > > +
> > > + buf = cpu_to_be32(value);
> > > + migrate_send_rp_message(mis, MIG_RP_CMD_PONG, 4, (uint8_t *)&buf);
> >
> > It occurs to me that you could define PONG as returning the whole
> > buffer that PING sends, instead of just 4-bytes. Might allow for some
> > more testing of variable sized messages.
>
> Yes; although it would complicate things a lot if I made it fully generic
> because I'd have to worry about allocating a buffer etc and I'm not
> making vast use of the 4 bytes I've already got.
Couldn't migrate_send_rp_pong just take a buf pointer and length, then
you can point that directly at the buffer in the ping message you've
received.
--
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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