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, 116 insertions, 0 deletions

diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
new file mode 100644
index 000000000..cdd431027
--- /dev/null
+++ b/drivers/firmware/efi/tpm.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 Google, Inc.
+ *     Thiebaud Weksteen <tweek@google.com>
+ */
+
+#define TPM_MEMREMAP(start, size) early_memremap(start, size)
+#define TPM_MEMUNMAP(start, size) early_memunmap(start, size)
+
+#include <asm/early_ioremap.h>
+#include <linux/efi.h>
+#include <linux/init.h>
+#include <linux/memblock.h>
+#include <linux/tpm_eventlog.h>
+
+int efi_tpm_final_log_size;
+EXPORT_SYMBOL(efi_tpm_final_log_size);
+
+static int __init tpm2_calc_event_log_size(void *data, int count, void *size_info)
+{
+	struct tcg_pcr_event2_head *header;
+	u32 event_size, size = 0;
+
+	while (count > 0) {
+		header = data + size;
+		event_size = __calc_tpm2_event_size(header, size_info, true);
+		if (event_size == 0)
+			return -1;
+		size += event_size;
+		count--;
+	}
+
+	return size;
+}
+
+/*
+ * Reserve the memory associated with the TPM Event Log configuration table.
+ */
+int __init efi_tpm_eventlog_init(void)
+{
+	struct linux_efi_tpm_eventlog *log_tbl;
+	struct efi_tcg2_final_events_table *final_tbl;
+	unsigned int tbl_size;
+	int final_tbl_size;
+	int ret = 0;
+
+	if (efi.tpm_log == EFI_INVALID_TABLE_ADDR) {
+		/*
+		 * We can't calculate the size of the final events without the
+		 * first entry in the TPM log, so bail here.
+		 */
+		return 0;
+	}
+
+	log_tbl = early_memremap(efi.tpm_log, sizeof(*log_tbl));
+	if (!log_tbl) {
+		pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
+		       efi.tpm_log);
+		efi.tpm_log = EFI_INVALID_TABLE_ADDR;
+		return -ENOMEM;
+	}
+
+	tbl_size = sizeof(*log_tbl) + log_tbl->size;
+	if (memblock_reserve(efi.tpm_log, tbl_size)) {
+		pr_err("TPM Event Log memblock reserve fails (0x%lx, 0x%x)\n",
+		       efi.tpm_log, tbl_size);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) {
+		pr_info("TPM Final Events table not present\n");
+		goto out;
+	} else if (log_tbl->version != EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) {
+		pr_warn(FW_BUG "TPM Final Events table invalid\n");
+		goto out;
+	}
+
+	final_tbl = early_memremap(efi.tpm_final_log, sizeof(*final_tbl));
+
+	if (!final_tbl) {
+		pr_err("Failed to map TPM Final Event Log table @ 0x%lx\n",
+		       efi.tpm_final_log);
+		efi.tpm_final_log = EFI_INVALID_TABLE_ADDR;
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	final_tbl_size = 0;
+	if (final_tbl->nr_events != 0) {
+		void *events = (void *)efi.tpm_final_log
+				+ sizeof(final_tbl->version)
+				+ sizeof(final_tbl->nr_events);
+
+		final_tbl_size = tpm2_calc_event_log_size(events,
+							  final_tbl->nr_events,
+							  log_tbl->log);
+	}
+
+	if (final_tbl_size < 0) {
+		pr_err(FW_BUG "Failed to parse event in TPM Final Events Log\n");
+		ret = -EINVAL;
+		goto out_calc;
+	}
+
+	memblock_reserve(efi.tpm_final_log,
+			 final_tbl_size + sizeof(*final_tbl));
+	efi_tpm_final_log_size = final_tbl_size;
+
+out_calc:
+	early_memunmap(final_tbl, sizeof(*final_tbl));
+out:
+	early_memunmap(log_tbl, sizeof(*log_tbl));
+	return ret;
+}
+