KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 173 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-rbd b/Documentation/ABI/testing/sysfs-bus-rbd
new file mode 100644
index 000000000..417a2fe21
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-rbd
@@ -0,0 +1,173 @@
+What:		/sys/bus/rbd/add
+Date:		Oct, 2010
+KernelVersion:	v2.6.37
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(WO) Add rbd block device.
+
+		Usage: <mon ip addr> <options> <pool name> <rbd image name> [<snap name>]
+
+		Example::
+
+		 $ echo "192.168.0.1 name=admin rbd foo" > /sys/bus/rbd/add
+
+		The snapshot name can be "-" or omitted to map the image
+		read/write. A <dev-id> will be assigned for any registered block
+		device. If snapshot is used, it will be mapped read-only.
+
+
+What:		/sys/bus/rbd/remove
+Date:		Oct, 2010
+KernelVersion:	v2.6.37
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(WO) Remove rbd block device.
+
+		Usage: <dev-id> [force]
+
+		Example::
+
+		 $ echo 2 > /sys/bus/rbd/remove
+
+		Optional "force" argument which when passed will wait for
+		running requests and then unmap the image. Requests sent to the
+		driver after initiating the removal will be failed. (August
+		2016, since 4.9.)
+
+
+What:		/sys/bus/rbd/add_single_major
+Date:		Dec, 2013
+KernelVersion:	v3.14
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(WO) Available only if rbd module is inserted with single_major
+		parameter set to true.
+
+		Usage is the same as for /sys/bus/rbd/add. If present, this
+		should be used instead of the latter: any attempts to use
+		/sys/bus/rbd/add if /sys/bus/rbd/add_single_major is available
+		will fail for backwards compatibility reasons.
+
+
+What:		/sys/bus/rbd/remove_single_major
+Date:		Dec, 2013
+KernelVersion:	v3.14
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(WO) Available only if rbd module is inserted with single_major
+		parameter set to true.
+
+		Usage is the same as for /sys/bus/rbd/remove. If present, this
+		should be used instead of the latter: any attempts to use
+		/sys/bus/rbd/remove if /sys/bus/rbd/remove_single_major is
+		available will fail for backwards compatibility reasons.
+
+
+What:		/sys/bus/rbd/supported_features
+Date:		Mar, 2017
+KernelVersion:	v4.11
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(RO) Displays the features supported by the rbd module so that
+		userspace can generate meaningful error messages and spell out
+		unsupported features that need to be disabled.
+
+
+What:		/sys/bus/rbd/devices/<dev-id>/size
+What:		/sys/bus/rbd/devices/<dev-id>/major
+What:		/sys/bus/rbd/devices/<dev-id>/client_id
+What:		/sys/bus/rbd/devices/<dev-id>/pool
+What:		/sys/bus/rbd/devices/<dev-id>/name
+What:		/sys/bus/rbd/devices/<dev-id>/refresh
+What:		/sys/bus/rbd/devices/<dev-id>/current_snap
+Date:		Oct, 2010
+KernelVersion:	v2.6.37
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+
+		==============	================================================
+		size		(RO) The size (in bytes) of the mapped block
+				device.
+
+		major		(RO) The block device major number.
+
+		client_id	(RO) The ceph unique client id that was assigned
+				for this specific session.
+
+		pool		(RO) The name of the storage pool where this rbd
+				image resides. An rbd image name is unique
+				within its pool.
+
+		name		(RO) The name of the rbd image.
+
+		refresh		(WO) Writing to this file will reread the image
+				header data and set all relevant data structures
+				accordingly.
+
+		current_snap	(RO) The current snapshot for which the device
+				is mapped.
+		==============	================================================
+
+
+What:		/sys/bus/rbd/devices/<dev-id>/pool_id
+Date:		Jul, 2012
+KernelVersion:	v3.6
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(RO) The unique identifier for the rbd image's pool. This is a
+		permanent attribute of the pool. A pool's id will never change.
+
+
+What:		/sys/bus/rbd/devices/<dev-id>/image_id
+What:		/sys/bus/rbd/devices/<dev-id>/features
+Date:		Oct, 2012
+KernelVersion:	v3.7
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		=========	===============================================
+		image_id	(RO) The unique id for the rbd image. (For rbd
+				image format 1 this is empty.)
+
+		features	(RO) A hexadecimal encoding of the feature bits
+				for this image.
+		=========	===============================================
+
+
+What:		/sys/bus/rbd/devices/<dev-id>/parent
+Date:		Nov, 2012
+KernelVersion:	v3.8
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(RO) Information identifying the chain of parent images in a
+		layered rbd image. Entries are separated by empty lines.
+
+
+What:		/sys/bus/rbd/devices/<dev-id>/minor
+Date:		Dec, 2013
+KernelVersion:	v3.14
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		(RO) The block device minor number.
+
+
+What:		/sys/bus/rbd/devices/<dev-id>/snap_id
+What:		/sys/bus/rbd/devices/<dev-id>/config_info
+What:		/sys/bus/rbd/devices/<dev-id>/cluster_fsid
+What:		/sys/bus/rbd/devices/<dev-id>/client_addr
+Date:		Aug, 2016
+KernelVersion:	v4.9
+Contact:	Sage Weil <sage@newdream.net>
+Description:
+		============	================================================
+		snap_id		(RO) The current snapshot's id.
+
+		config_info	(RO) The string written into
+				/sys/bus/rbd/add{,_single_major}.
+
+		cluster_fsid	(RO) The ceph cluster UUID.
+
+		client_addr	(RO) The ceph unique client
+				entity_addr_t (address + nonce). The format is
+				<address>:<port>/<nonce>: '1.2.3.4:1234/5678' or
+				'[1:2:3:4:5:6:7:8]:1234/5678'.
+		============	================================================