[coreboot-gerrit] Change in coreboot[master]: security/intel/stm: Check for processor STM support

[Nico Huber (Code Review)]

Nico Huber has submitted this change. ( https://review.coreboot.org/c/coreboot/+/38836 )

Change subject: security/intel/stm: Check for processor STM support
......................................................................

security/intel/stm: Check for processor STM support

Check to ensure that dual monitor mode is supported on the
current processor. Dual monitor mode is normally supported on
any Intel x86 processor that has VTx support.  The STM is
a hypervisor that executes in SMM dual monitor mode.  This
check should fail only in the rare case were dual monitor mode
is disabled.  If the check fails, then the STM will not
be initialized by coreboot.

Signed-off-by: Eugene D. Myers 
Change-Id: I518bb2aa1bdec94b5b6d5e991d7575257f3dc6e9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38836
Tested-by: build bot (Jenkins) 
Reviewed-by: Nico Huber 
---
M src/include/cpu/x86/msr.h
M src/security/intel/stm/StmPlatformSmm.c
2 files changed, 12 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Nico Huber: Looks good to me, approved

diff --git a/src/include/cpu/x86/msr.h b/src/include/cpu/x86/msr.h
index 49abd41..c761bc0 100644
--- a/src/include/cpu/x86/msr.h
+++ b/src/include/cpu/x86/msr.h
@@ -74,6 +74,7 @@
 #define  MCA_STATUS_LO_ERRCODE_EXT_MASK	(0x3f << MCA_STATUS_LO_ERRCODE_EXT_SH)
 #define  MCA_STATUS_LO_ERRCODE_MASK	(0xffff << 0)
 #define IA32_VMX_BASIC_MSR              0x480
+#define  VMX_BASIC_HI_DUAL_MONITOR      (1UL << (49 - 32))
 #define IA32_VMX_MISC_MSR               0x485
 #define MC0_ADDR			0x402
 #define MC0_MISC			0x403
diff --git a/src/security/intel/stm/StmPlatformSmm.c b/src/security/intel/stm/StmPlatformSmm.c
index d7064b0..45db0e0 100644
--- a/src/security/intel/stm/StmPlatformSmm.c
+++ b/src/security/intel/stm/StmPlatformSmm.c
@@ -159,9 +159,20 @@
 {
    msr_t InitMseg;
    msr_t MsegChk;
+	msr_t vmx_basic;
+
    uintptr_t addr_calc;  // used to calculate the stm resource heap area

printk(BIOS_DEBUG, "STM: set up for cpu %d/%d\n", cpu, num_cpus);
+
+	vmx_basic = rdmsr(IA32_VMX_BASIC_MSR);
+
+	// Does this processor support an STM?
+	if ((vmx_basic.hi & VMX_BASIC_HI_DUAL_MONITOR) != VMX_BASIC_HI_DUAL_MONITOR) {
+		printk(BIOS_WARNING, "STM: not supported on CPU %d\n", cpu);
+		return;
+	}
+
    if (cpu == 0) {

// need to create the BIOS resource list once