x86/bus_lock: Add support for AMD

JIRA: https://issues.redhat.com/browse/RHEL-50321

commit 408eb74
Author: Ravi Bangoria <ravi.bangoria@amd.com>
Date:   Thu Aug 8 06:29:35 2024 +0000

    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

Signed-off-by: John Allen <johnalle@redhat.com>

Author: John Allen

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

@@ -2434,7 +2434,7 @@ 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

@@ -1849,6 +1849,8 @@ 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

@@ -612,7 +612,6 @@ static void init_intel(struct cpuinfo_x86 *c)
 	init_intel_misc_features(c);
 
 	split_lock_init();
-	bus_lock_init();
 
 	intel_init_thermal(c);
 }