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, 46 insertions, 0 deletions

diff --git a/Documentation/networking/x25.rst b/Documentation/networking/x25.rst
new file mode 100644
index 000000000..e11d9ebdf
--- /dev/null
+++ b/Documentation/networking/x25.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+Linux X.25 Project
+==================
+
+As my third year dissertation at University I have taken it upon myself to
+write an X.25 implementation for Linux. My aim is to provide a complete X.25
+Packet Layer and a LAPB module to allow for "normal" X.25 to be run using
+Linux. There are two sorts of X.25 cards available, intelligent ones that
+implement LAPB on the card itself, and unintelligent ones that simply do
+framing, bit-stuffing and checksumming. These both need to be handled by the
+system.
+
+I therefore decided to write the implementation such that as far as the
+Packet Layer is concerned, the link layer was being performed by a lower
+layer of the Linux kernel and therefore it did not concern itself with
+implementation of LAPB. Therefore the LAPB modules would be called by
+unintelligent X.25 card drivers and not by intelligent ones, this would
+provide a uniform device driver interface, and simplify configuration.
+
+To confuse matters a little, an 802.2 LLC implementation is also possible
+which could allow X.25 to be run over an Ethernet (or Token Ring) and
+conform with the JNT "Pink Book", this would have a different interface to
+the Packet Layer but there would be no confusion since the class of device
+being served by the LLC would be completely separate from LAPB.
+
+Just when you thought that it could not become more confusing, another
+option appeared, XOT. This allows X.25 Packet Layer frames to operate over
+the Internet using TCP/IP as a reliable link layer. RFC1613 specifies the
+format and behaviour of the protocol. If time permits this option will also
+be actively considered.
+
+A linux-x25 mailing list has been created at vger.kernel.org to support the
+development and use of Linux X.25. It is early days yet, but interested
+parties are welcome to subscribe to it. Just send a message to
+majordomo@vger.kernel.org with the following in the message body:
+
+subscribe linux-x25
+end
+
+The contents of the Subject line are ignored.
+
+Jonathan
+
+g4klx@g4klx.demon.co.uk