x86/bus_lock: Add support for AMD

Add Bus Lock Detect (called Bus Lock Trap in AMD docs) support for AMD
platforms. Bus Lock Detect is enumerated with CPUID Fn0000_0007_ECX_x0
bit [24 / BUSLOCKTRAP]. It can be enabled through MSR_IA32_DEBUGCTLMSR.
When enabled, hardware clears DR6[11] and raises a #DB exception on
occurrence of Bus Lock if CPL > 0. More detail about the feature can be
found in AMD APM[1].

[1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June
     2023, Vol 2, 13.1.3.6 Bus Lock Trap
     https://bugzilla.kernel.org/attachment.cgi?id=304653

Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/all/20240808062937.1149-3-ravi.bangoria@amd.com

Author: Ravi Bangoria

Documentation/arch/x86/buslock.rst

@@ -26,7 +26,8 @@ Detection
 =========
 
 Intel processors may support either or both of the following hardware
-mechanisms to detect split locks and bus locks.
+mechanisms to detect split locks and bus locks. Some AMD processors also
+support bus lock detect.
 
 #AC exception for split lock detection
 --------------------------------------

arch/x86/Kconfig

@@ -2428,7 +2428,7 @@ source "kernel/livepatch/Kconfig"
 
 config X86_BUS_LOCK_DETECT
 	bool "Split Lock Detect and Bus Lock Detect support"
-	depends on CPU_SUP_INTEL
+	depends on CPU_SUP_INTEL || CPU_SUP_AMD
 	default y
 	help
 	  Enable Split Lock Detect and Bus Lock Detect functionalities.

arch/x86/kernel/cpu/common.c

@@ -1832,6 +1832,8 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 	if (this_cpu->c_init)
 		this_cpu->c_init(c);
 
+	bus_lock_init();
+
 	/* Disable the PN if appropriate */
 	squash_the_stupid_serial_number(c);
 

arch/x86/kernel/cpu/intel.c

@@ -610,7 +610,6 @@ static void init_intel(struct cpuinfo_x86 *c)
 	init_intel_misc_features(c);
 
 	split_lock_init();
-	bus_lock_init();
 
 	intel_init_thermal(c);
 }