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, 50 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/reset.c b/arch/m68k/coldfire/reset.c
new file mode 100644
index 000000000..6e5f8ab39
--- /dev/null
+++ b/arch/m68k/coldfire/reset.c
@@ -0,0 +1,50 @@
+/*
+ * reset.c  -- common ColdFire SoC reset support
+ *
+ * (C) Copyright 2012, Greg Ungerer <gerg@uclinux.org>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <asm/machdep.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+
+/*
+ *	There are 2 common methods amongst the ColdFure parts for reseting
+ *	the CPU. But there are couple of exceptions, the 5272 and the 547x
+ *	have something completely special to them, and we let their specific
+ *	subarch code handle them.
+ */
+
+#ifdef MCFSIM_SYPCR
+static void mcf_cpu_reset(void)
+{
+	local_irq_disable();
+	/* Set watchdog to soft reset, and enabled */
+	mcf_write8(0xc0, MCFSIM_SYPCR);
+	for (;;)
+		/* wait for watchdog to timeout */;
+}
+#endif
+
+#ifdef MCF_RCR
+static void mcf_cpu_reset(void)
+{
+	local_irq_disable();
+	mcf_write8(MCF_RCR_SWRESET, MCF_RCR);
+}
+#endif
+
+static int __init mcf_setup_reset(void)
+{
+	mach_reset = mcf_cpu_reset;
+	return 0;
+}
+
+arch_initcall(mcf_setup_reset);