[PATCH] Support for GUEST_SMBASE vmcs field for nested virtualization

[Matthias Lange <mlange@sec.t-labs.tu-berlin.de>]

Hi,

the following patch adds support for the GUEST_SMBASE field in the VMCS for
the case of nested virtualization. There are hypervisors that try to access
that mandatory field. The patch avoids returning a "unsupported vmcs field"
error to the L1 hypervisor by adding the GUEST_SMBASE field into the vmcs12
struct.

Regards,
Matthias.

---
 arch/x86/include/asm/vmx.h |    1 +
 arch/x86/kvm/vmx.c         |    6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

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 32eb588..88e21e9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -294,7 +294,8 @@ struct __packed vmcs12 {
 	u32 guest_activity_state;
 	u32 guest_sysenter_cs;
 	u32 host_ia32_sysenter_cs;
-	u32 padding32[8]; /* room for future expansion */
+	u32 guest_smbase;
+	u32 padding32[7]; /* room for future expansion */
 	u16 virtual_processor_id;
 	u16 guest_es_selector;
 	u16 guest_cs_selector;
@@ -556,6 +557,7 @@ 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),
@@ -6536,6 +6538,7 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 	vmcs_write32(GUEST_INTERRUPTIBILITY_INFO,
 		vmcs12->guest_interruptibility_info);
 	vmcs_write32(GUEST_ACTIVITY_STATE, vmcs12->guest_activity_state);
+	vmcs_write32(GUEST_SMBASE, vmcs12->guest_smbase);
 	vmcs_write32(GUEST_SYSENTER_CS, vmcs12->guest_sysenter_cs);
 	vmcs_writel(GUEST_DR7, vmcs12->guest_dr7);
 	vmcs_writel(GUEST_RFLAGS, vmcs12->guest_rflags);
@@ -6937,6 +6940,7 @@ void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 	vmcs12->guest_idtr_base = vmcs_readl(GUEST_IDTR_BASE);
 
 	vmcs12->guest_activity_state = vmcs_read32(GUEST_ACTIVITY_STATE);
+	vmcs12->guest_smbase = vmcs_read32(GUEST_SMBASE);
 	vmcs12->guest_interruptibility_info =
 		vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
 	vmcs12->guest_pending_dbg_exceptions =
-- 
1.7.9.5


-- 
Dipl.-Inf. Matthias Lange <mlange@sec.t-labs.tu-berlin.de>
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