soc/intel/common/block/sgx: Fix crash in MP init

On Hyper-Threading enabled platforms the MSR_PRMRR_PHYS_MASK was written
when already locked by the sibling thread. In addition it loads microcode
updates on all threads.

To prevent such race conditions only call the code on one thread, such
that the MSRs are only written once per core and the microcode is only
loaded once for each core.

Also add comments that describe the scope of the MSR that is being
written to and mention the Intel documents used for reference.

Fixes crash in SGX MP init.
Tested on Supermicro X11SSH-TF.

Change-Id: I7102da028a449c60ca700b3f9ccda9017aa6d6b5
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35312
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

2 files changed, 50 insertions, 6 deletions

diff --git a/src/soc/intel/common/block/sgx/Kconfig b/src/soc/intel/common/block/sgx/Kconfig
index 0852bfbf49..ffd501a7e2 100644
--- a/src/soc/intel/common/block/sgx/Kconfig
+++ b/src/soc/intel/common/block/sgx/Kconfig
@@ -1,5 +1,7 @@
 config SOC_INTEL_COMMON_BLOCK_SGX
 	bool
+	select CPU_INTEL_COMMON
+	select CPU_INTEL_COMMON_HYPERTHREADING
 	default n
 	help
 	 Software Guard eXtension(SGX) Feature. Intel SGX is a set of new CPU
diff --git a/src/soc/intel/common/block/sgx/sgx.c b/src/soc/intel/common/block/sgx/sgx.c
index 0edf50f09b..377a71994f 100644
--- a/src/soc/intel/common/block/sgx/sgx.c
+++ b/src/soc/intel/common/block/sgx/sgx.c
@@ -17,6 +17,7 @@
 #include <cpu/x86/msr.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/intel/microcode.h>
+#include <cpu/intel/common/common.h>
 #include <intelblocks/mp_init.h>
 #include <intelblocks/msr.h>
 #include <intelblocks/sgx.h>
@@ -54,9 +55,18 @@ void prmrr_core_configure(void)
 	} prmrr_base, prmrr_mask;
 	msr_t msr;
 
-	if (!is_sgx_supported())
+	/*
+	 * Software Developer's Manual Volume 4:
+	 * Order Number: 335592-068US
+	 * Chapter 2.16.1
+	 * MSR_PRMRR_PHYS_MASK is in scope "Core"
+	 * MSR_PRMRR_PHYS_BASE is in scope "Core"
+	 * Return if Hyper-Threading is enabled and not thread 0
+	 */
+	if (!is_sgx_supported() || intel_ht_sibling())
 		return;
 
+	/* PRMRR_PHYS_MASK is in scope "Core" */
 	msr = rdmsr(MSR_PRMRR_PHYS_MASK);
 	/* If it is locked don't attempt to write PRMRR MSRs. */
 	if (msr.lo & PRMRR_PHYS_MASK_LOCK)
@@ -109,6 +119,12 @@ static void enable_sgx(void)
 {
 	msr_t msr;
 
+	/*
+	 * Intel 64 and IA-32 ArchitecturesSoftware Developer's ManualVolume 3C
+	 * Order Number:  326019-060US
+	 * Chapter 35.10.2 "Additional MSRs Supported by Intel"
+	 * IA32_FEATURE_CONTROL is in scope "Thread"
+	 */
 	msr = rdmsr(IA32_FEATURE_CONTROL);
 	/* Only enable it when it is not locked */
 	if ((msr.lo & FEATURE_CONTROL_LOCK_BIT) == 0) {
@@ -121,6 +137,12 @@ static void lock_sgx(void)
 {
 	msr_t msr;
 
+	/*
+	 * Intel 64 and IA-32 ArchitecturesSoftware Developer's ManualVolume 3C
+	 * Order Number:  326019-060US
+	 * Chapter 35.10.2 "Additional MSRs Supported by Intel"
+	 * IA32_FEATURE_CONTROL is in scope "Thread"
+	 */
 	msr = rdmsr(IA32_FEATURE_CONTROL);
 	/* If it is locked don't attempt to lock it again. */
 	if ((msr.lo & 1) == 0) {
@@ -135,6 +157,7 @@ static int owner_epoch_update(void)
 	 * for PoC just write '0's to the MSRs. */
 	msr_t msr = {0, 0};
 
+	/* SGX_OWNEREPOCH is in scope "Package" */
 	wrmsr(MSR_SGX_OWNEREPOCH0, msr);
 	wrmsr(MSR_SGX_OWNEREPOCH1, msr);
 	return 0;
@@ -175,16 +198,19 @@ static int is_prmrr_approved(void)
 	return 0;
 }
 
+/*
+ * Configures SGX according to "Intel Software Guard Extensions Technology"
+ * Document Number: 565432
+ */
 void sgx_configure(void *unused)
 {
-	const void *microcode_patch = intel_mp_current_microcode();
 
 	if (!is_sgx_supported() || !is_prmrr_set()) {
 		printk(BIOS_ERR, "SGX: pre-conditions not met\n");
 		return;
 	}
 
-	/* Enable the SGX feature */
+	/* Enable the SGX feature on all threads. */
 	enable_sgx();
 
 	/* Update the owner epoch value */
@@ -194,10 +220,26 @@ void sgx_configure(void *unused)
 	/* Ensure to lock memory before reload microcode patch */
 	cpu_lock_sgx_memory();
 
-	/* Reload the microcode patch */
-	intel_microcode_load_unlocked(microcode_patch);
+	/*
+	 * Update just on the first CPU in the core. Other siblings
+	 * get the update automatically according to Document: 253668-060US
+	 * Intel SDM Chapter 9.11.6.3
+	 * "Update in a System Supporting Intel Hyper-Threading Technology"
+	 * Intel Hyper-Threading Technology has implications on the loading of the
+	 * microcode update. The update must be loaded for each core in a physical
+	 * processor. Thus, for a processor supporting Intel Hyper-Threading
+	 * Technology, only one logical processor per core is required to load the
+	 * microcode update. Each individual logical processor can independently
+	 * load the update. However, MP initialization must provide some mechanism
+	 * (e.g. a software semaphore) to force serialization of microcode update
+	 * loads and to prevent simultaneous load attempts to the same core.
+	 */
+	if (!intel_ht_sibling()) {
+		const void *microcode_patch = intel_mp_current_microcode();
+		intel_microcode_load_unlocked(microcode_patch);
+	}
 
-	/* Lock the SGX feature */
+	/* Lock the SGX feature on all threads. */
 	lock_sgx();
 
 	/* Activate the SGX feature, if PRMRR config was approved by MCHECK */