File 0293-migration-warn-about-inconsistent-s.patch of Package qemu.12301

From ba8de6248f62786578ccc4604f43d05ef7314bca Mon Sep 17 00:00:00 2001
From: Bruce Rogers <brogers@suse.com>
Date: Wed, 21 Feb 2018 14:00:52 -0700
Subject: [PATCH] migration: warn about inconsistent spec_ctrl state

As an attempt to help the user do the right thing, warn if we
detect spec_ctrl data in the migration stream, but where the
cpu defined doesn't have the feature. This would indicate the
migration is from the quick and dirty qemu produced in January
2018 to handle Spectre v2. That qemu version exposed the IBRS
cpu feature to all vcpu types, which helped in the short term
but wasn't a well designed approach.
Warn the user that the now migrated guest needs to be restarted
as soon as possible, using the spec_ctrl cpu feature flag or a
*-IBRS vcpu model specified as appropriate.

Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 cpus.c                | 12 ++++++++++++
 include/qemu/thread.h |  1 +
 migration/migration.c |  8 ++++++++
 3 files changed, 21 insertions(+)

diff --git a/cpus.c b/cpus.c
index e6dcae31f5..685b416f2a 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1544,6 +1544,18 @@ exit:
     fclose(f);
 }
 
+bool spec_ctrl_is_inconsistent(void)
+{
+#if defined(TARGET_I386)
+    X86CPU *x86_cpu = X86_CPU(current_cpu);
+    CPUX86State *env = x86_cpu != NULL ? &x86_cpu->env : NULL;
+    if (env && !(env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_SPEC_CTRL) &&
+	    env->spec_ctrl)
+        return true;
+#endif
+    return false;
+}
+
 void qmp_inject_nmi(Error **errp)
 {
 #if defined(TARGET_I386)
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index 5114ec8e79..83f1e165c9 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -62,4 +62,5 @@ struct Notifier;
 void qemu_thread_atexit_add(struct Notifier *notifier);
 void qemu_thread_atexit_remove(struct Notifier *notifier);
 
+bool spec_ctrl_is_inconsistent(void);
 #endif
diff --git a/migration/migration.c b/migration/migration.c
index bc424907f3..aedb2c0ea7 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -655,6 +655,14 @@ static void *migration_thread(void *opaque)
                 if (!qemu_file_get_error(s->file)) {
                     migrate_set_state(s, MIGRATION_STATUS_ACTIVE,
                                       MIGRATION_STATUS_COMPLETED);
+                    if (spec_ctrl_is_inconsistent()) {
+                    fprintf(stderr, "WARNING! Migration from qemu with rudimentary "
+                                    "Spectre v2 support to newer qemu\ndetected! To "
+                                    "maintain proper protection, restart the guest as "
+                                    "soon as possible\nusing the spec_ctrl cpu feature "
+                                    "flag or a *-IBRS vcpu model specified\nas appropriate."
+                                    "\n");
+                    }
                     break;
                 }
             }