migration: Add documentation for fdset with multifd + file

With the last few changes to the fdset infrastructure, we now allow
multifd to use an fdset when migrating to a file. This is useful for
th

migration: Add documentation for fdset with multifd + file

With the last few changes to the fdset infrastructure, we now allow
multifd to use an fdset when migrating to a file. This is useful for
the scenario where the management layer wants to have control over the
migration file.

By receiving the file descriptors directly, QEMU can delegate some
high level operating system operations to the management layer (such
as mandatory access control). The management layer might also want to
add its own headers before the migration stream.

Document the "file:/dev/fdset/#" syntax for the multifd migration with
mapped-ram. The requirements for the fdset mechanism are:

- the fdset must contain two fds that are not duplicates between
themselves;

- if direct-io is to be used, exactly one of the fds must have the
O_DIRECT flag set;

- the file must be opened with WRONLY on the migration source side;

- the file must be opened with RDONLY on the migration destination
side.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

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migration: Remove block migration

The block migration has been considered obsolete since QEMU 8.2 in
favor of the more flexible storage migration provided by the
blockdev-mirror driver. Two releases

migration: Remove block migration

The block migration has been considered obsolete since QEMU 8.2 in
favor of the more flexible storage migration provided by the
blockdev-mirror driver. Two releases have passed so now it's time to
remove it.

Deprecation commit 66db46ca83 ("migration: Deprecate block
migration").

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

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migration/multifd: Don't fsync when closing QIOChannelFile

Commit bc38feddeb ("io: fsync before closing a file channel") added a
fsync/fdatasync at the closing point of the QIOChannelFile to ensure

migration/multifd: Don't fsync when closing QIOChannelFile

Commit bc38feddeb ("io: fsync before closing a file channel") added a
fsync/fdatasync at the closing point of the QIOChannelFile to ensure
integrity of the migration stream in case of QEMU crash.

The decision to do the sync at qio_channel_close() was not the best
since that function runs in the main thread and the fsync can cause
QEMU to hang for several minutes, depending on the migration size and
disk speed.

To fix the hang, remove the fsync from qio_channel_file_close().

At this moment, the migration code is the only user of the fsync and
we're taking the tradeoff of not having a sync at all, leaving the
responsibility to the upper layers.

Fixes: bc38feddeb ("io: fsync before closing a file channel")
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240305195629.9922-1-farosas@suse.de
Link: https://lore.kernel.org/r/20240305174332.2553-1-farosas@suse.de
[peterx: add more comment to the qio_channel_close()]
Signed-off-by: Peter Xu <peterx@redhat.com>

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docs/devel/migration.rst: Document the file transport

When adding the support for file migration with the file: transport,
we missed adding documentation for it.

Signed-off-by: Fabiano Rosas <faros

docs/devel/migration.rst: Document the file transport

When adding the support for file migration with the file: transport,
we missed adding documentation for it.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240220224138.24759-2-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>

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exec/ioport: Add portio_list_set_enabled()

Some SuperI/O devices such as the VIA south bridges or the PC87312 controller
allow to enable or disable their SuperI/O functions. Add a convenience functi

exec/ioport: Add portio_list_set_enabled()

Some SuperI/O devices such as the VIA south bridges or the PC87312 controller
allow to enable or disable their SuperI/O functions. Add a convenience function
for implementing this in the VIA south bridges.

The naming of the functions is inspired by its memory_region_set_enabled()
pendant.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20240114123911.4877-7-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

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exec/ioport: Add portio_list_set_address()

Some SuperI/O devices such as the VIA south bridges or the PC87312 controller
are able to relocate their SuperI/O functions. Add a convenience function for

exec/ioport: Add portio_list_set_address()

Some SuperI/O devices such as the VIA south bridges or the PC87312 controller
are able to relocate their SuperI/O functions. Add a convenience function for
implementing this in the VIA south bridges.

This convenience function relies on previous simplifications in exec/ioport
which avoids some duplicate synchronization of I/O port base addresses. The
naming of the function is inspired by its memory_region_set_address() pendant.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20240114123911.4877-6-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

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docs/migration: Split "dirty limit"

Split that into a separate file, put under "features".

Cc: Yong Huang <yong.huang@smartx.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.k

docs/migration: Split "dirty limit"

Split that into a separate file, put under "features".

Cc: Yong Huang <yong.huang@smartx.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240109064628.595453-8-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

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docs/migration: Split "Postcopy"

Split postcopy into a separate file. Introduce a head page "features.rst"
to keep all the features on top of migration framework.

Reviewed-by: Cédric Le Goater <cl

docs/migration: Split "Postcopy"

Split postcopy into a separate file. Introduce a head page "features.rst"
to keep all the features on top of migration framework.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240109064628.595453-7-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

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docs/migration: Split "Debugging" and "Firmware"

Move the two sections into a separate file called "best-practices.rst".
Add the entry into index.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Lin

docs/migration: Split "Debugging" and "Firmware"

Move the two sections into a separate file called "best-practices.rst".
Add the entry into index.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240109064628.595453-6-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

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docs/migration: Split "Backwards compatibility" separately

Split the section from main.rst into a separate file. Reference it in the
index.rst.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link:

docs/migration: Split "Backwards compatibility" separately

Split the section from main.rst into a separate file. Reference it in the
index.rst.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240109064628.595453-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

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docs/migration: Create index page

Create an index page for migration module. Move VFIO migration there too.
A trivial touch-up on the title to use lower case there.

Since then we'll have "migratio

docs/migration: Create index page

Create an index page for migration module. Move VFIO migration there too.
A trivial touch-up on the title to use lower case there.

Since then we'll have "migration" as the top title, make the main doc file
renamed to "migration framework".

Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240109064628.595453-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

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docs/migration: Create migration/ directory

Migration documentation is growing into a single file too large. Create a
sub-directory for it for a split.

We also already have separate vfio/virtio do

docs/migration: Create migration/ directory

Migration documentation is growing into a single file too large. Create a
sub-directory for it for a split.

We also already have separate vfio/virtio documentations, move it all over
into the directory.

Note that the virtio one is still not yet converted to rST. That is a job
for later.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240109064628.595453-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

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