File 0446-migration-warn-about-inconsistent-s.patch of Package qemu.9344
From e1a2358e950b97a58e44e3eddb5e89a58c99eacc 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.c | 8 ++++++++
3 files changed, 21 insertions(+)
diff --git a/cpus.c b/cpus.c
index 485d02ccca..4ee6df99c6 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1476,6 +1476,18 @@ 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 f7e3b9b290..9cd0ef5a06 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -61,4 +61,5 @@ bool qemu_thread_is_self(QemuThread *thread);
void qemu_thread_exit(void *retval);
void qemu_thread_naming(bool enable);
+bool spec_ctrl_is_inconsistent(void);
#endif
diff --git a/migration.c b/migration.c
index 26f4b65e0f..b391a8304f 100644
--- a/migration.c
+++ b/migration.c
@@ -614,6 +614,14 @@ static void *migration_thread(void *opaque)
if (!qemu_file_get_error(s->file)) {
migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_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;
}
}
