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, 120 insertions, 0 deletions

diff --git a/Documentation/sphinx-static/theme_overrides.css b/Documentation/sphinx-static/theme_overrides.css
new file mode 100644
index 000000000..79000b26e
--- /dev/null
+++ b/Documentation/sphinx-static/theme_overrides.css
@@ -0,0 +1,120 @@
+/* -*- coding: utf-8; mode: css -*-
+ *
+ * Sphinx HTML theme customization: read the doc
+ * Please don't add any color definition here, as the theme should
+ * work for both normal and dark modes.
+ */
+
+/* Improve contrast and increase size for easier reading. */
+
+body {
+	font-family: serif;
+	font-size: 100%;
+}
+
+h1, h2, .rst-content .toctree-wrapper p.caption, h3, h4, h5, h6, legend {
+	font-family: sans-serif;
+}
+
+div[class^="highlight"] pre {
+	font-family: monospace;
+	font-size: 100%;
+}
+
+.wy-menu-vertical {
+	font-family: sans-serif;
+}
+
+.c {
+	font-style: normal;
+}
+
+p {
+	font-size: 100%;
+}
+
+/* Interim: Code-blocks with line nos - lines and line numbers don't line up.
+ * see: https://github.com/rtfd/sphinx_rtd_theme/issues/419
+ */
+
+div[class^="highlight"] pre {
+    line-height: normal;
+}
+.rst-content .highlight > pre {
+    line-height: normal;
+}
+
+/* Keep fields from being strangely far apart due to inheirited table CSS. */
+.rst-content table.field-list th.field-name {
+    padding-top: 1px;
+    padding-bottom: 1px;
+}
+.rst-content table.field-list td.field-body {
+    padding-top: 1px;
+    padding-bottom: 1px;
+}
+
+@media screen {
+
+    /* content column
+     *
+     * RTD theme's default is 800px as max width for the content, but we have
+     * tables with tons of columns, which need the full width of the view-port.
+     */
+
+    .wy-nav-content{max-width: none; }
+
+    /* table:
+     *
+     *   - Sequences of whitespace should collapse into a single whitespace.
+     *   - make the overflow auto (scrollbar if needed)
+     *   - align caption "left" ("center" is unsuitable on vast tables)
+     */
+
+    .wy-table-responsive table td { white-space: normal; }
+    .wy-table-responsive { overflow: auto; }
+    .rst-content table.docutils caption { text-align: left; font-size: 100%; }
+
+    /* captions:
+     *
+     *   - captions should have 100% (not 85%) font size
+     *   - hide the permalink symbol as long as link is not hovered
+     */
+
+    caption, .wy-table caption, .rst-content table.field-list caption {
+        font-size: 100%;
+    }
+    caption a.headerlink { opacity: 0; }
+    caption a.headerlink:hover { opacity: 1; }
+
+    /* Menu selection and keystrokes */
+
+    span.menuselection {
+	font-family: "Courier New", Courier, monospace
+    }
+
+    code.kbd, code.kbd span {
+	font-weight: bold;
+	font-family: "Courier New", Courier, monospace
+    }
+
+    /* fix bottom margin of lists items */
+
+    .rst-content .section ul li:last-child, .rst-content .section ul li p:last-child {
+          margin-bottom: 12px;
+    }
+
+    /* inline literal: drop the borderbox, padding and red color */
+
+    code, .rst-content tt, .rst-content code {
+        color: inherit;
+        border: none;
+        padding: unset;
+        background: inherit;
+        font-size: 85%;
+    }
+
+    .rst-content tt.literal,.rst-content tt.literal,.rst-content code.literal {
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+    }
+}