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, 45 insertions, 0 deletions

diff --git a/arch/m68k/Kconfig.debug b/arch/m68k/Kconfig.debug
new file mode 100644
index 000000000..d036f9038
--- /dev/null
+++ b/arch/m68k/Kconfig.debug
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config BOOTPARAM
+	bool "Compiled-in Kernel Boot Parameter"
+
+config BOOTPARAM_STRING
+	string "Kernel Boot Parameter"
+	default "console=ttyS0,19200"
+	depends on BOOTPARAM
+
+config EARLY_PRINTK
+	bool "Early printk"
+	depends on MMU_MOTOROLA
+	help
+	  Write kernel log output directly to a serial port.
+	  Where implemented, output goes to the framebuffer as well.
+	  PROM console functionality on Sun 3x is not affected by this option.
+
+	  Pass "earlyprintk" on the kernel command line to get a
+	  boot console.
+
+	  This is useful for kernel debugging when your machine crashes very
+	  early, i.e. before the normal console driver is loaded.
+	  You should normally say N here, unless you want to debug such a crash.
+
+if !MMU
+
+config FULLDEBUG
+	bool "Full Symbolic/Source Debugging support"
+	help
+	  Enable debugging symbols on kernel build.
+
+config HIGHPROFILE
+	bool "Use fast second timer for profiling"
+	depends on COLDFIRE
+	help
+	  Use a fast secondary clock to produce profiling information.
+
+config BDM_DISABLE
+	bool "Disable BDM signals"
+	depends on COLDFIRE
+	help
+	  Disable the ColdFire CPU's BDM signals.
+
+endif