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, 76 insertions, 0 deletions

diff --git a/tools/testing/selftests/clock-helpers.h b/tools/testing/selftests/clock-helpers.h
new file mode 100644
index 000000000..01451f538
--- /dev/null
+++ b/tools/testing/selftests/clock-helpers.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __CLOCK_HELPERS_H
+#define __CLOCK_HELPERS_H
+
+#include <sys/types.h>
+#include <time.h>
+
+#define MSEC_PER_SEC	1000LL
+#define USEC_PER_MSEC	1000LL
+#define NSEC_PER_USEC	1000LL
+#define NSEC_PER_MSEC	1000000LL
+#define USEC_PER_SEC	1000000LL
+#define NSEC_PER_SEC	1000000000LL
+#define PSEC_PER_SEC	1000000000000LL
+#define FSEC_PER_SEC	1000000000000000LL
+
+#ifndef CLOCK_AUX
+#define CLOCK_AUX	16
+#endif
+
+#ifndef MAX_AUX_CLOCKS
+#define MAX_AUX_CLOCKS	8
+#endif
+
+#ifndef CLOCK_AUX_LAST
+#define CLOCK_AUX_LAST	(CLOCK_AUX + MAX_AUX_CLOCKS - 1)
+#endif
+
+__attribute__((unused))
+static inline const char *clock_name(clockid_t clockid)
+{
+	switch (clockid) {
+	case CLOCK_REALTIME:
+		return "CLOCK_REALTIME";
+	case CLOCK_MONOTONIC:
+		return "CLOCK_MONOTONIC";
+	case CLOCK_PROCESS_CPUTIME_ID:
+		return "CLOCK_PROCESS_CPUTIME_ID";
+	case CLOCK_THREAD_CPUTIME_ID:
+		return "CLOCK_THREAD_CPUTIME_ID";
+	case CLOCK_MONOTONIC_RAW:
+		return "CLOCK_MONOTONIC_RAW";
+	case CLOCK_REALTIME_COARSE:
+		return "CLOCK_REALTIME_COARSE";
+	case CLOCK_MONOTONIC_COARSE:
+		return "CLOCK_MONOTONIC_COARSE";
+	case CLOCK_BOOTTIME:
+		return "CLOCK_BOOTTIME";
+	case CLOCK_REALTIME_ALARM:
+		return "CLOCK_REALTIME_ALARM";
+	case CLOCK_BOOTTIME_ALARM:
+		return "CLOCK_BOOTTIME_ALARM";
+	case CLOCK_TAI:
+		return "CLOCK_TAI";
+	case CLOCK_AUX + 0:
+		return "CLOCK_AUX0";
+	case CLOCK_AUX + 1:
+		return "CLOCK_AUX1";
+	case CLOCK_AUX + 2:
+		return "CLOCK_AUX2";
+	case CLOCK_AUX + 3:
+		return "CLOCK_AUX3";
+	case CLOCK_AUX + 4:
+		return "CLOCK_AUX4";
+	case CLOCK_AUX + 5:
+		return "CLOCK_AUX5";
+	case CLOCK_AUX + 6:
+		return "CLOCK_AUX6";
+	case CLOCK_AUX + 7:
+		return "CLOCK_AUX7";
+	};
+	return "UNKNOWN_CLOCKID";
+}
+
+#endif /* __CLOCK_HELPERS_H */