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/userspace-api/media/intro.rst b/Documentation/userspace-api/media/intro.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+============
+Introduction
+============
+
+This document covers the Linux Kernel to Userspace API's used by video
+and radio streaming devices, including video cameras, analog and digital
+TV receiver cards, AM/FM receiver cards, Software Defined Radio (SDR),
+streaming capture and output devices, codec devices and remote controllers.
+
+A typical media device hardware is shown at :ref:`typical_media_device`.
+
+.. _typical_media_device:
+
+.. kernel-figure:: typical_media_device.svg
+    :alt:   typical_media_device.svg
+    :align: center
+
+    Typical Media Device
+
+The media infrastructure API was designed to control such devices. It is
+divided into five parts.
+
+1. The :ref:`first part <v4l2spec>` covers radio, video capture and output,
+   cameras, analog TV devices and codecs.
+
+2. The :ref:`second part <dvbapi>` covers the API used for digital TV and
+   Internet reception via one of the several digital tv standards. While it is
+   called as DVB API, in fact it covers several different video standards
+   including DVB-T/T2, DVB-S/S2, DVB-C, ATSC, ISDB-T, ISDB-S, DTMB, etc. The
+   complete list of supported standards can be found at
+   :c:type:`fe_delivery_system`.
+
+3. The :ref:`third part <remote_controllers>` covers the Remote Controller API.
+
+4. The :ref:`fourth part <media_controller>` covers the Media Controller API.
+
+5. The :ref:`fifth part <cec>` covers the CEC (Consumer Electronics Control) API.
+
+It should also be noted that a media device may also have audio components, like
+mixers, PCM capture, PCM playback, etc, which are controlled via ALSA API.  For
+additional information and for the latest development code, see:
+`https://linuxtv.org <https://linuxtv.org>`__.  For discussing improvements,
+reporting troubles, sending new drivers, etc, please mail to: `Linux Media
+Mailing List (LMML) <http://vger.kernel.org/vger-lists.html#linux-media>`__.