On Wed, Nov 16, 2022 at 04:49:18PM +0530, manish.mishra wrote: > > On 16/11/22 12:20 am, Daniel P. Berrangé wrote: > > On Tue, Nov 15, 2022 at 06:11:30PM +0000, Daniel P. Berrangé wrote: > > > On Mon, Nov 07, 2022 at 04:51:59PM +0000, manish.mishra wrote: > > > > Current logic assumes that channel connections on the destination side > > > > are > > > > always established in the same order as the source and the first one > > > > will > > > > always be the main channel followed by the multifid or post-copy > > > > preemption channel. This may not be always true, as even if a channel > > > > has a > > > > connection established on the source side it can be in the pending > > > > state on > > > > the destination side and a newer connection can be established first. > > > > Basically causing out of order mapping of channels on the destination > > > > side. > > > > Currently, all channels except post-copy preempt send a magic number, > > > > this > > > > patch uses that magic number to decide the type of channel. This logic > > > > is > > > > applicable only for precopy(multifd) live migration, as mentioned, the > > > > post-copy preempt channel does not send any magic number. Also, tls live > > > > migrations already does tls handshake before creating other channels, so > > > > this issue is not possible with tls, hence this logic is avoided for tls > > > > live migrations. This patch uses MSG_PEEK to check the magic number of > > > > channels so that current data/control stream management remains > > > > un-effected. > > > > > > > > Suggested-by: Daniel P. Berrangé<berra...@redhat.com> > > > > Signed-off-by: manish.mishra<manish.mis...@nutanix.com> > > > > > > > > v2: > > > > TLS does not support MSG_PEEK, so V1 was broken for tls live > > > > migrations. For tls live migration, while initializing main channel > > > > tls handshake is done before we can create other channels, so this > > > > issue is not possible for tls live migrations. In V2 added a check > > > > to avoid checking magic number for tls live migration and fallback > > > > to older method to decide mapping of channels on destination side. > > > > --- > > > > include/io/channel.h | 25 +++++++++++++++++++++++ > > > > io/channel-socket.c | 27 ++++++++++++++++++++++++ > > > > io/channel.c | 39 +++++++++++++++++++++++++++++++++++ > > > > migration/migration.c | 44 +++++++++++++++++++++++++++++----------- > > > > migration/multifd.c | 12 ++++------- > > > > migration/multifd.h | 2 +- > > > > migration/postcopy-ram.c | 5 +---- > > > > migration/postcopy-ram.h | 2 +- > > > > 8 files changed, 130 insertions(+), 26 deletions(-) > > > This should be two commits, because the 'io' and 'migration' > > > code are two separate subsystems in QEMU. > > > > > > > diff --git a/include/io/channel.h b/include/io/channel.h > > > > index c680ee7480..74177aeeea 100644 > > > > --- a/include/io/channel.h > > > > +++ b/include/io/channel.h > > > > @@ -115,6 +115,10 @@ struct QIOChannelClass { > > > > int **fds, > > > > size_t *nfds, > > > > Error **errp); > > > > + ssize_t (*io_read_peek)(QIOChannel *ioc, > > > > + void *buf, > > > > + size_t nbytes, > > > > + Error **errp); > > > This API should be called "io_read_peekv" and use > > > "const struct iovec *iov", such that is matches the > > > design of 'io_readv'. > > > > > > There should also be a QIOChannelFeature flag > > > registered to indicate whether a given channel > > > impl supports peeking at data. > > > > > > > > > > @@ -475,6 +479,27 @@ int qio_channel_write_all(QIOChannel *ioc, > > > > size_t buflen, > > > > Error **errp); > > > > +/** > > > > + * qio_channel_read_peek_all: > > > > + * @ioc: the channel object > > > > + * @buf: the memory region to read in data > > > > + * @nbytes: the number of bytes to read > > > > + * @errp: pointer to a NULL-initialized error object > > > > + * > > > > + * Read given @nbytes data from peek of channel into > > > > + * memory region @buf. > > > > + * > > > > + * The function will be blocked until read size is > > > > + * equal to requested size. > > > > + * > > > > + * Returns: 1 if all bytes were read, 0 if end-of-file > > > > + * occurs without data, or -1 on error > > > > + */ > > > > +int qio_channel_read_peek_all(QIOChannel *ioc, > > > > + void* buf, > > > > + size_t nbytes, > > > > + Error **errp); > > > There should be qio_channel_read_peek, qio_channel_read_peekv, > > > qio_channel_read_peek_all and qio_channel_read_peekv_all. > > Actually ignore that. We should not add any new APIs at > > all. Instead the io_readv callback, and the qio_channel_read*all() > > methods should gain a 'int flags' parameter, in the same way that > > the write methods have one. Then there should be as > > QIO_CHANNEL_READ_FLAG_PEEK constant defined. > > Hi Daniel, As MSG_PEEK always reads from top even if there were > previos partial reads, so current |qio_channel_readv_all_eofmay > not work? I can keep things upto ||qio_channel_readv as common > for both with flags parameters but have separate > ||qio_channel_readv_peek_all_eof? Does something like that works.|||
Simplest is probably to just not add 'flags' to the 'all' variants, just the non-'all' varants. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|