From 59c1aecdd92dc66e92f8ffe8a2a5e121031a2ae7 Mon Sep 17 00:00:00 2001

From: Eduardo Habkost <ehabkost@redhat.com>

Date: Fri, 21 Dec 2018 00:31:11 +0100

Subject: [PATCH 1/2] i386: Deprecate arch-facilities and make it block live

 migration

RH-Author: Eduardo Habkost <ehabkost@redhat.com>

Message-id: <20181221003111.32374-1-ehabkost@redhat.com>

Patchwork-id: 83733

O-Subject: [RHEL-7.7 qemu-kvm PATCH] i386: Deprecate arch-facilities and make it block live migration

Bugzilla: 1658407

RH-Acked-by: Bandan Das <bsd@redhat.com>

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

RH-Acked-by: Jiri Denemark <jdenemar@redhat.com>

The arch-facilities feature flag is being deprecated because it

was never supported upstream.  The upstream property is

called "arch-capabilities", but it was not backported to

RHEL7/qemu-kvm.

Note that arch-capabilities is not required for mitigation of

CVE-2017-5715.

In addition to being deprecated, arch-facilities will now block

live migration because the value of MSR_IA32_ARCH_CAPABILITIES is

host-dependent and not migration-safe.

Note that the "arch-facilities" option didn't work in RHEL-7.5.

It only started working (by accident) on RHEL-7.6, after the KVM

kernel module code was updated to report the feature flag on

GET_SUPPORTED_CPUID.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 target-i386/cpu.c | 35 +++++++++++++++++++++++++++++++++++

 target-i386/cpu.h |  1 +

 2 files changed, 36 insertions(+)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c

index 4b3a238e8d..a36483eca9 100644

--- a/target-i386/cpu.c

+++ b/target-i386/cpu.c

@@ -34,6 +34,7 @@

 #include "qapi-visit.h"

 #include "qapi/visitor.h"

 #include "sysemu/arch_init.h"

+#include "migration/migration.h"

 #include "hw/hw.h"

 #if defined(CONFIG_KVM)

@@ -1742,6 +1743,14 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)

                                          wi->cpuid_reg);

     }

+    /*

+     * Features that won't be enabled automatically by "-cpu host" even if

+     * reported by GET_SUPPORTED_CPUID:

+     */

+

+    /* arch-facilities: deprecated (see comment on x86_cpu_realizefn()) */

+    x86_cpu_def->features[FEAT_7_0_EDX] &= ~CPUID_7_0_EDX_ARCH_CAPABILITIES;

+

 #endif /* CONFIG_KVM */

 }

@@ -3089,6 +3098,32 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)

 #endif

     }

+    /*

+     * RHEL-only:

+     *

+     * The arch-facilities feature flag is deprecated because it was never

+     * supported upstream.  The upstream property is "arch-capabilities",

+     * but it was not backported to this QEMU version.  Note that

+     * arch-capabilities is not required for mitigation of CVE-2017-5715.

+     *

+     * In addition to being deprecated, arch-facilities blocks live migration

+     * because the value of MSR_IA32_ARCH_CAPABILITIES is host-dependent and

+     * not migration-safe.

+     */

+    if (cpu->env.features[FEAT_7_0_EDX] & CPUID_7_0_EDX_ARCH_CAPABILITIES) {

+        static bool warned = false;

+        static Error *arch_facilities_blocker;

+        if (!warned) {

+            error_setg(&arch_facilities_blocker,

+                       "The arch-facilities CPU feature is deprecated and "

+                       "does not support live migration");

+            migrate_add_blocker(arch_facilities_blocker);

+            error_report("WARNING: the arch-facilities CPU feature is "

+                         "deprecated and does not support live migration");

+            warned = true;

+        }

+    }

+

 #ifndef CONFIG_USER_ONLY

     qemu_register_reset(x86_cpu_machine_reset_cb, cpu);

diff --git a/target-i386/cpu.h b/target-i386/cpu.h

index debb0e5bf4..73437f16c5 100644

--- a/target-i386/cpu.h

+++ b/target-i386/cpu.h

@@ -597,6 +597,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];

 #define CPUID_7_0_EDX_AVX512_4VNNIW (1U << 2) /* AVX512 Neural Network Instructions */

 #define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */

 #define CPUID_7_0_EDX_SPEC_CTRL     (1U << 26) /* Indirect Branch - Restrict Speculation */

+#define CPUID_7_0_EDX_ARCH_CAPABILITIES (1U << 29)  /*Arch Capabilities*/

 #define CPUID_7_0_EDX_SPEC_CTRL_SSBD  (1U << 31) /* Speculative Store Bypass Disable */

 #define CPUID_8000_0008_EBX_IBPB    (1U << 12) /* Indirect Branch Prediction Barrier */

-- 

2.19.1