KVM: VMX: enable VMXON check with SMX enabled (Intel TXT)

Per document, for feature control MSR:

  Bit 1 enables VMXON in SMX operation. If the bit is clear, execution
        of VMXON in SMX operation causes a general-protection exception.
  Bit 2 enables VMXON outside SMX operation. If the bit is clear, execution
        of VMXON outside SMX operation causes a general-protection exception.

This patch is to enable this kind of check with SMX for VMXON in KVM.

Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

4 files changed, 26 insertions, 13 deletions

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index bc473acfa7f9..f9324851eba0 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -202,8 +202,9 @@
 #define MSR_IA32_EBL_CR_POWERON         0x0000002a
 #define MSR_IA32_FEATURE_CONTROL        0x0000003a
 
-#define FEATURE_CONTROL_LOCKED          (1<<0)
-#define FEATURE_CONTROL_VMXON_ENABLED   (1<<2)
+#define FEATURE_CONTROL_LOCKED                          (1<<0)
+#define FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX        (1<<1)
+#define FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX       (1<<2)
 
 #define MSR_IA32_APICBASE               0x0000001b
 #define MSR_IA32_APICBASE_BSP           (1<<8)
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 86c9f91b48ae..46b827778d16 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -46,6 +46,7 @@
 
 /* Global pointer to shared data; NULL means no measured launch. */
 struct tboot *tboot __read_mostly;
+EXPORT_SYMBOL(tboot);
 
 /* timeout for APs (in secs) to enter wait-for-SIPI state during shutdown */
 #define AP_WAIT_TIMEOUT         1
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c4f3955c64e0..d2a47aefdee7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -27,6 +27,7 @@
 #include <linux/moduleparam.h>
 #include <linux/ftrace_event.h>
 #include <linux/slab.h>
+#include <linux/tboot.h>
 #include "kvm_cache_regs.h"
 #include "x86.h"
 
@@ -1272,9 +1273,16 @@ static __init int vmx_disabled_by_bios(void)
         u64 msr;
 
         rdmsrl(MSR_IA32_FEATURE_CONTROL, msr);
-        return (msr & (FEATURE_CONTROL_LOCKED |
-                       FEATURE_CONTROL_VMXON_ENABLED))
-            == FEATURE_CONTROL_LOCKED;
+        if (msr & FEATURE_CONTROL_LOCKED) {
+                if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX)
+                        && tboot_enabled())
+                        return 1;
+                if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX)
+                        && !tboot_enabled())
+                        return 1;
+        }
+
+        return 0;
         /* locked but not enabled */
 }
 
@@ -1282,21 +1290,23 @@ static int hardware_enable(void *garbage)
 {
         int cpu = raw_smp_processor_id();
         u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
-        u64 old;
+        u64 old, test_bits;
 
         if (read_cr4() & X86_CR4_VMXE)
                 return -EBUSY;
 
         INIT_LIST_HEAD(&per_cpu(vcpus_on_cpu, cpu));
         rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
-        if ((old & (FEATURE_CONTROL_LOCKED |
-                    FEATURE_CONTROL_VMXON_ENABLED))
-            != (FEATURE_CONTROL_LOCKED |
-                FEATURE_CONTROL_VMXON_ENABLED))
+
+        test_bits = FEATURE_CONTROL_LOCKED;
+        test_bits |= FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
+        if (tboot_enabled())
+                test_bits |= FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX;
+
+        if ((old & test_bits) != test_bits) {
                 /* enable and lock */
-                wrmsrl(MSR_IA32_FEATURE_CONTROL, old |
-                       FEATURE_CONTROL_LOCKED |
-                       FEATURE_CONTROL_VMXON_ENABLED);
+                wrmsrl(MSR_IA32_FEATURE_CONTROL, old | test_bits);
+        }
         write_cr4(read_cr4() | X86_CR4_VMXE); /* FIXME: not cpu hotplug safe */
         asm volatile (ASM_VMX_VMXON_RAX
                       : : "a"(&phys_addr), "m"(phys_addr)
diff --git a/include/linux/tboot.h b/include/linux/tboot.h
index bf2a0c748878..1dba6ee55203 100644
--- a/include/linux/tboot.h
+++ b/include/linux/tboot.h
@@ -150,6 +150,7 @@ extern int tboot_force_iommu(void);
 
 #else
 
+#define tboot_enabled()                 0
 #define tboot_probe()                   do { } while (0)
 #define tboot_shutdown(shutdown_type)   do { } while (0)
 #define tboot_sleep(sleep_state, pm1a_control, pm1b_control)    \