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, 81 insertions, 0 deletions

diff --git a/drivers/input/input-compat.h b/drivers/input/input-compat.h
new file mode 100644
index 000000000..99c87ceb9
--- /dev/null
+++ b/drivers/input/input-compat.h
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _INPUT_COMPAT_H
+#define _INPUT_COMPAT_H
+
+/*
+ * 32bit compatibility wrappers for the input subsystem.
+ *
+ * Very heavily based on evdev.c - Copyright (c) 1999-2002 Vojtech Pavlik
+ */
+
+#include <linux/compiler.h>
+#include <linux/compat.h>
+#include <linux/input.h>
+
+#ifdef CONFIG_COMPAT
+
+struct input_event_compat {
+	compat_ulong_t sec;
+	compat_ulong_t usec;
+	__u16 type;
+	__u16 code;
+	__s32 value;
+};
+
+struct ff_periodic_effect_compat {
+	__u16 waveform;
+	__u16 period;
+	__s16 magnitude;
+	__s16 offset;
+	__u16 phase;
+
+	struct ff_envelope envelope;
+
+	__u32 custom_len;
+	compat_uptr_t custom_data;
+};
+
+struct ff_effect_compat {
+	__u16 type;
+	__s16 id;
+	__u16 direction;
+	struct ff_trigger trigger;
+	struct ff_replay replay;
+
+	union {
+		struct ff_constant_effect constant;
+		struct ff_ramp_effect ramp;
+		struct ff_periodic_effect_compat periodic;
+		struct ff_condition_effect condition[2]; /* One for each axis */
+		struct ff_rumble_effect rumble;
+	} u;
+};
+
+static inline size_t input_event_size(void)
+{
+	return (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) ?
+		sizeof(struct input_event_compat) : sizeof(struct input_event);
+}
+
+#else
+
+static inline size_t input_event_size(void)
+{
+	return sizeof(struct input_event);
+}
+
+#endif /* CONFIG_COMPAT */
+
+int input_event_from_user(const char __user *buffer,
+			 struct input_event *event);
+
+int input_event_to_user(char __user *buffer,
+			const struct input_event *event);
+
+int input_ff_effect_from_user(const char __user *buffer, size_t size,
+			      struct ff_effect *effect);
+
+int input_bits_to_string(char *buf, int buf_size, unsigned long bits,
+                         bool skip_empty);
+
+#endif /* _INPUT_COMPAT_H */