File 0034-migration-warn-about-inconsistent-s.patch of Package qemu

Overview Repositories Revisions Requests Users Attributes Meta

File 0034-migration-warn-about-inconsistent-s.patch of Package qemu (Revision 26b4ccd251a37375ccfdab11ac40164b)

Currently displaying revision 26b4ccd251a37375ccfdab11ac40164b , Show latest

From c82bb4d1c7daf2c41d3a7e6d44f26cab65b138f9 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 6fa701e423..b57038fda5 100644
--- a/cpus.c
+++ b/cpus.c
@@ -2326,6 +2326,18 @@ 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)
 {
     nmi_monitor_handle(monitor_get_cpu_index(), errp);
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index ef7bd16123..c4ecb386fe 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -240,4 +240,5 @@ void qemu_lockcnt_inc_and_unlock(QemuLockCnt *lockcnt);
  */
 unsigned qemu_lockcnt_count(QemuLockCnt *lockcnt);
 
+bool spec_ctrl_is_inconsistent(void);
 #endif
diff --git a/migration/migration.c b/migration/migration.c
index 52a5092add..3cf11aadfa 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2163,6 +2163,14 @@ static void migration_completion(MigrationState *s)
         migrate_set_state(&s->state, current_active_state,
                           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");
+    }
 
     return;

Places

File 0034-migration-warn-about-inconsistent-s.patch of Package qemu (Revision 26b4ccd251a37375ccfdab11ac40164b)

Places