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, 47 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/dbc.h b/drivers/crypto/ccp/dbc.h
new file mode 100644
index 000000000..e0fecbe92
--- /dev/null
+++ b/drivers/crypto/ccp/dbc.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Platform Security Processor (PSP) Dynamic Boost Control support
+ *
+ * Copyright (C) 2023 Advanced Micro Devices, Inc.
+ *
+ * Author: Mario Limonciello <mario.limonciello@amd.com>
+ */
+
+#ifndef __DBC_H__
+#define __DBC_H__
+
+#include <uapi/linux/psp-dbc.h>
+
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/psp-platform-access.h>
+
+#include "psp-dev.h"
+
+struct psp_dbc_device {
+	struct device *dev;
+	struct psp_device *psp;
+
+	union dbc_buffer *mbox;
+
+	struct mutex ioctl_mutex;
+
+	struct miscdevice char_dev;
+
+	/* used to abstract communication path */
+	bool	use_ext;
+	u32	header_size;
+	u32	*payload_size;
+	u32	*result;
+	void	*payload;
+};
+
+union dbc_buffer {
+	struct psp_request		pa_req;
+	struct psp_ext_request		ext_req;
+};
+
+void dbc_dev_destroy(struct psp_device *psp);
+int dbc_dev_init(struct psp_device *psp);
+
+#endif /* __DBC_H */