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/sfs.h b/drivers/crypto/ccp/sfs.h
new file mode 100644
index 000000000..97704c210
--- /dev/null
+++ b/drivers/crypto/ccp/sfs.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Platform Security Processor (PSP) Seamless Firmware (SFS) Support.
+ *
+ * Copyright (C) 2025 Advanced Micro Devices, Inc.
+ *
+ * Author: Ashish Kalra <ashish.kalra@amd.com>
+ */
+
+#ifndef __SFS_H__
+#define __SFS_H__
+
+#include <uapi/linux/psp-sfs.h>
+
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/psp-sev.h>
+#include <linux/psp-platform-access.h>
+#include <linux/set_memory.h>
+
+#include "psp-dev.h"
+
+struct sfs_misc_dev {
+	struct kref refcount;
+	struct miscdevice misc;
+};
+
+struct sfs_command {
+	struct psp_ext_req_buffer_hdr hdr;
+	u8 buf[PAGE_SIZE - sizeof(struct psp_ext_req_buffer_hdr)];
+	u8 sfs_buffer[];
+} __packed;
+
+struct sfs_device {
+	struct device *dev;
+	struct psp_device *psp;
+
+	struct page *page;
+	struct sfs_command *command_buf;
+
+	struct sfs_misc_dev *misc;
+};
+
+void sfs_dev_destroy(struct psp_device *psp);
+int sfs_dev_init(struct psp_device *psp);
+
+#endif /* __SFS_H__ */