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From 8cafea931977e494797584610664279ea21ef427 Mon Sep 17 00:00:00 2001
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From: Eduardo Habkost <ehabkost@redhat.com>
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Date: Fri, 21 Dec 2018 00:31:11 +0100
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Subject: [PATCH] i386: Deprecate arch-facilities and make it block live
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migration
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RH-Author: Eduardo Habkost <ehabkost@redhat.com>
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Message-id: <20181221003111.32374-1-ehabkost@redhat.com>
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Patchwork-id: 83733
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O-Subject: [RHEL-7.7 qemu-kvm PATCH] i386: Deprecate arch-facilities and make it block live migration
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Bugzilla: 1664792
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RH-Acked-by: Bandan Das <bsd@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Jiri Denemark <jdenemar@redhat.com>
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The arch-facilities feature flag is being deprecated because it
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was never supported upstream. The upstream property is
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called "arch-capabilities", but it was not backported to
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RHEL7/qemu-kvm.
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Note that arch-capabilities is not required for mitigation of
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CVE-2017-5715.
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In addition to being deprecated, arch-facilities will now block
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live migration because the value of MSR_IA32_ARCH_CAPABILITIES is
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host-dependent and not migration-safe.
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Note that the "arch-facilities" option didn't work in RHEL-7.5.
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It only started working (by accident) on RHEL-7.6, after the KVM
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kernel module code was updated to report the feature flag on
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GET_SUPPORTED_CPUID.
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Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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target-i386/cpu.c | 35 +++++++++++++++++++++++++++++++++++
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target-i386/cpu.h | 1 +
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2 files changed, 36 insertions(+)
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diff --git a/target-i386/cpu.c b/target-i386/cpu.c
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index 4b3a238e8d..a36483eca9 100644
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--- a/target-i386/cpu.c
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+++ b/target-i386/cpu.c
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@@ -34,6 +34,7 @@
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#include "qapi-visit.h"
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#include "qapi/visitor.h"
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#include "sysemu/arch_init.h"
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+#include "migration/migration.h"
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#include "hw/hw.h"
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#if defined(CONFIG_KVM)
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@@ -1742,6 +1743,14 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
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wi->cpuid_reg);
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}
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+ /*
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+ * Features that won't be enabled automatically by "-cpu host" even if
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+ * reported by GET_SUPPORTED_CPUID:
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+ */
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+
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+ /* arch-facilities: deprecated (see comment on x86_cpu_realizefn()) */
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+ x86_cpu_def->features[FEAT_7_0_EDX] &= ~CPUID_7_0_EDX_ARCH_CAPABILITIES;
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+
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#endif /* CONFIG_KVM */
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}
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@@ -3089,6 +3098,32 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
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#endif
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}
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+ /*
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+ * RHEL-only:
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+ *
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+ * The arch-facilities feature flag is deprecated because it was never
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+ * supported upstream. The upstream property is "arch-capabilities",
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+ * but it was not backported to this QEMU version. Note that
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+ * arch-capabilities is not required for mitigation of CVE-2017-5715.
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+ *
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+ * In addition to being deprecated, arch-facilities blocks live migration
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+ * because the value of MSR_IA32_ARCH_CAPABILITIES is host-dependent and
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+ * not migration-safe.
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+ */
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+ if (cpu->env.features[FEAT_7_0_EDX] & CPUID_7_0_EDX_ARCH_CAPABILITIES) {
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+ static bool warned = false;
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+ static Error *arch_facilities_blocker;
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+ if (!warned) {
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+ error_setg(&arch_facilities_blocker,
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+ "The arch-facilities CPU feature is deprecated and "
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+ "does not support live migration");
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+ migrate_add_blocker(arch_facilities_blocker);
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+ error_report("WARNING: the arch-facilities CPU feature is "
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+ "deprecated and does not support live migration");
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+ warned = true;
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+ }
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+ }
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+
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#ifndef CONFIG_USER_ONLY
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qemu_register_reset(x86_cpu_machine_reset_cb, cpu);
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diff --git a/target-i386/cpu.h b/target-i386/cpu.h
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index debb0e5bf4..73437f16c5 100644
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--- a/target-i386/cpu.h
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+++ b/target-i386/cpu.h
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@@ -597,6 +597,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
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#define CPUID_7_0_EDX_AVX512_4VNNIW (1U << 2) /* AVX512 Neural Network Instructions */
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#define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
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#define CPUID_7_0_EDX_SPEC_CTRL (1U << 26) /* Indirect Branch - Restrict Speculation */
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+#define CPUID_7_0_EDX_ARCH_CAPABILITIES (1U << 29) /*Arch Capabilities*/
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#define CPUID_7_0_EDX_SPEC_CTRL_SSBD (1U << 31) /* Speculative Store Bypass Disable */
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#define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */
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--
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2.19.1
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