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, 122 insertions, 0 deletions

diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
new file mode 100644
index 000000000..a4e139dee
--- /dev/null
+++ b/tools/objtool/objtool.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <subcmd/exec-cmd.h>
+#include <subcmd/pager.h>
+#include <linux/kernel.h>
+
+#include <objtool/builtin.h>
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+
+static struct objtool_file file;
+
+struct objtool_file *objtool_open_read(const char *filename)
+{
+	if (file.elf) {
+		ERROR("won't handle more than one file at a time");
+		return NULL;
+	}
+
+	file.elf = elf_open_read(filename, O_RDWR);
+	if (!file.elf)
+		return NULL;
+
+	hash_init(file.insn_hash);
+	INIT_LIST_HEAD(&file.retpoline_call_list);
+	INIT_LIST_HEAD(&file.return_thunk_list);
+	INIT_LIST_HEAD(&file.static_call_list);
+	INIT_LIST_HEAD(&file.mcount_loc_list);
+	INIT_LIST_HEAD(&file.endbr_list);
+	INIT_LIST_HEAD(&file.call_list);
+	file.ignore_unreachables = opts.no_unreachable;
+	file.hints = false;
+
+	return &file;
+}
+
+int objtool_pv_add(struct objtool_file *f, int idx, struct symbol *func)
+{
+	if (!opts.noinstr)
+		return 0;
+
+	if (!f->pv_ops) {
+		ERROR("paravirt confusion");
+		return -1;
+	}
+
+	/*
+	 * These functions will be patched into native code,
+	 * see paravirt_patch().
+	 */
+	if (!strcmp(func->name, "_paravirt_nop") ||
+	    !strcmp(func->name, "_paravirt_ident_64"))
+		return 0;
+
+	/* already added this function */
+	if (!list_empty(&func->pv_target))
+		return 0;
+
+	list_add(&func->pv_target, &f->pv_ops[idx].targets);
+	f->pv_ops[idx].clean = false;
+	return 0;
+}
+
+char *top_level_dir(const char *file)
+{
+	ssize_t len, self_len, file_len;
+	char self[PATH_MAX], *str;
+	int i;
+
+	len = readlink("/proc/self/exe", self, sizeof(self) - 1);
+	if (len <= 0)
+		return NULL;
+	self[len] = '\0';
+
+	for (i = 0; i < 3; i++) {
+		char *s = strrchr(self, '/');
+		if (!s)
+			return NULL;
+		*s = '\0';
+	}
+
+	self_len = strlen(self);
+	file_len = strlen(file);
+
+	str = malloc(self_len + file_len + 2);
+	if (!str)
+		return NULL;
+
+	memcpy(str, self, self_len);
+	str[self_len] = '/';
+	strcpy(str + self_len + 1, file);
+
+	return str;
+}
+
+int main(int argc, const char **argv)
+{
+	static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
+
+	if (init_signal_handler())
+		return -1;
+
+	/* libsubcmd init */
+	exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
+	pager_init(UNUSED);
+
+	if (argc > 1 && !strcmp(argv[1], "klp")) {
+		argc--;
+		argv++;
+		return cmd_klp(argc, argv);
+	}
+
+	return objtool_run(argc, argv);
+}