Hi,
I was playing around with kvm's nested virtualization feature on Intel
VT-x. When trying to access the GUEST_SMBASE (offset 0x4828)field of the
VMCS I got a "VMREAD/VMWRITE from/to unsupported VMCS component" error.
According to the Intel manual this field is not optional. The error
results from the "vmcs_field_to_offset" function in vmx.c because the
offset of GUEST_SMBASE is not defined.
The following patch adds support for the GUEST_SMBASE field. This allows
hypervisors running inside kvm read/write access to this field. I have
tested this to work on a Core i5 machine.
Best,
Matthias.
--
Dipl.-Inf. Matthias Lange <mlange@xxxxxxxxxxxxxxxxxxxxxxx>
Security in Telecommunications
TU Berlin / Telekom Innovation Laboratories
Ernst-Reuter-Platz 7, 10587 Berlin
Phone: +49 - 30 - 8353 58 553
Mobile: +49 - 160 - 587 28 07
Web: http://www.t-labs.tu-berlin.de/sect
From 266eaaea392db8ed9b94223785454124a2bd765e Mon Sep 17 00:00:00 2001
From: Matthias Lange <mlange@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Fri, 18 May 2012 10:58:00 +0200
Subject: [PATCH] Add support for the GUEST_SMBASE VMCS field for Intel VT-x.
According to the Intel manual this field is not optional.
---
arch/x86/include/asm/vmx.h | 1 +
arch/x86/kvm/vmx.c | 2 ++
2 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 31f180c..6a14720 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -194,6 +194,7 @@ enum vmcs_field {
GUEST_TR_AR_BYTES = 0x00004822,
GUEST_INTERRUPTIBILITY_INFO = 0x00004824,
GUEST_ACTIVITY_STATE = 0X00004826,
+ GUEST_SMBASE = 0x00004828,
GUEST_SYSENTER_CS = 0x0000482A,
HOST_IA32_SYSENTER_CS = 0x00004c00,
CR0_GUEST_HOST_MASK = 0x00006000,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4ff0ab9..0063743 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -285,6 +285,7 @@ struct __packed vmcs12 {
u32 guest_tr_ar_bytes;
u32 guest_interruptibility_info;
u32 guest_activity_state;
+ u32 guest_smbase;
u32 guest_sysenter_cs;
u32 host_ia32_sysenter_cs;
u32 padding32[8]; /* room for future expansion */
@@ -546,6 +547,7 @@ static unsigned short vmcs_field_to_offset_table[] = {
FIELD(GUEST_TR_BASE, guest_tr_base),
FIELD(GUEST_GDTR_BASE, guest_gdtr_base),
FIELD(GUEST_IDTR_BASE, guest_idtr_base),
+ FIELD(GUEST_SMBASE, guest_smbase),
FIELD(GUEST_DR7, guest_dr7),
FIELD(GUEST_RSP, guest_rsp),
FIELD(GUEST_RIP, guest_rip),
--
1.7.1
