linux-kernel - [RFC v2 22/26] KVM: x86/asi: Introduce address_space

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Message-Id: <1562855138-19507-23-git-send-email-alexandre.chartre@oracle.com>
Date:   Thu, 11 Jul 2019 16:25:34 +0200
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
To:     pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        kvm@...r.kernel.org, x86@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     konrad.wilk@...cle.com, jan.setjeeilers@...cle.com,
        liran.alon@...cle.com, jwadams@...gle.com, graf@...zon.de,
        rppt@...ux.vnet.ibm.com, alexandre.chartre@...cle.com
Subject: [RFC v2 22/26] KVM: x86/asi: Introduce address_space_isolation module parameter

From: Liran Alon <liran.alon@...cle.com>

Add the address_space_isolation parameter to the kvm module.

When set to true, KVM #VMExit handlers run in isolated address space
which maps only KVM required code and per-VM information instead of
entire kernel address space.

This mechanism is meant to mitigate memory-leak side-channels CPU
vulnerabilities (e.g. Spectre, L1TF and etc.) but can also be viewed
as security in-depth as it also helps generically against info-leaks
vulnerabilities in KVM #VMExit handlers and reduce the available
gadgets for ROP attacks.

This is set to false by default because it incurs a performance hit
which some users will not want to take for security gain.

Signed-off-by: Liran Alon <liran.alon@...cle.com>
Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/kvm/Makefile        |    3 ++-
 arch/x86/kvm/vmx/isolation.c |   26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletions(-)
 create mode 100644 arch/x86/kvm/vmx/isolation.c

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 31ecf7a..71579ed 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -12,7 +12,8 @@ kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
 			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
 			   hyperv.o page_track.o debugfs.o
 
-kvm-intel-y		+= vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o vmx/evmcs.o vmx/nested.o
+kvm-intel-y		+= vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
+			   vmx/evmcs.o vmx/nested.o vmx/isolation.o
 kvm-amd-y		+= svm.o pmu_amd.o
 
 obj-$(CONFIG_KVM)	+= kvm.o
diff --git a/arch/x86/kvm/vmx/isolation.c b/arch/x86/kvm/vmx/isolation.c
new file mode 100644
index 0000000..e25f663
--- /dev/null
+++ b/arch/x86/kvm/vmx/isolation.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ *
+ * KVM Address Space Isolation
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+/*
+ * When set to true, KVM #VMExit handlers run in isolated address space
+ * which maps only KVM required code and per-VM information instead of
+ * entire kernel address space.
+ *
+ * This mechanism is meant to mitigate memory-leak side-channels CPU
+ * vulnerabilities (e.g. Spectre, L1TF and etc.) but can also be viewed
+ * as security in-depth as it also helps generically against info-leaks
+ * vulnerabilities in KVM #VMExit handlers and reduce the available
+ * gadgets for ROP attacks.
+ *
+ * This is set to false by default because it incurs a performance hit
+ * which some users will not want to take for security gain.
+ */
+static bool __read_mostly address_space_isolation;
+module_param(address_space_isolation, bool, 0444);
-- 
1.7.1