soc/intel/tigerlake: Add SMRR Locking support

The SMRR MSRs can be locked, so that a further write to them will cause
a #GP.  This patch adds that functionality, but since the MSR is a
core-level register, it must only be done once per core; if the SoC has
hyperthreading enabled, then attempting to write the SMRR Lock bit on
the primary thread will cause a #GP when the secondary (sibling) thread
attempts to also write to this MSR.

BUG=b:164489598
TEST=Boot into OS, verify using `iotools rdmsr` that all threads have
the Lock bit set.

Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Change-Id: I4ae7c7f703bdf090144637d071eb810617d9e309
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45013
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kane Chen <kane.chen@intel.com>
Reviewed-by: Caveh Jalali <caveh@chromium.org>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/soc/intel/tigerlake/smmrelocate.c b/src/soc/intel/tigerlake/smmrelocate.c
index bbdcb68b10..e75e884464 100644
--- a/src/soc/intel/tigerlake/smmrelocate.c
+++ b/src/soc/intel/tigerlake/smmrelocate.c
@@ -9,6 +9,7 @@
 #include <cpu/x86/msr.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/x86/smm.h>
+#include <cpu/intel/common/common.h>
 #include <cpu/intel/em64t101_save_state.h>
 #include <cpu/intel/smm_reloc.h>
 #include <console/console.h>
@@ -137,8 +138,24 @@ void smm_relocation_handler(int cpu, uintptr_t curr_smbase,
 	/* Make appropriate changes to the save state map. */
 	update_save_state(cpu, curr_smbase, staggered_smbase, relo_params);
 
+	/*
+	 * The SMRR MSRs are core-level registers, so if two threads that share
+	 * a core try to both set the lock bit (in the same physical register),
+	 * a #GP will be raised on the second write to that register (which is
+	 * exactly what the lock is supposed to do), therefore secondary threads
+	 * should exit here.
+	 */
+	if (intel_ht_sibling())
+		return;
+
 	/* Write SMRR MSRs based on indicated support. */
 	mtrr_cap = rdmsr(MTRR_CAP_MSR);
+
+	/* Set Lock bit if supported */
+	if (mtrr_cap.lo & SMRR_LOCK_SUPPORTED)
+		relo_params->smrr_mask.lo |= SMRR_PHYS_MASK_LOCK;
+
+	/* Write SMRRs if supported */
 	if (mtrr_cap.lo & SMRR_SUPPORTED)
 		write_smrr(relo_params);
 }