linux-kernel - [PATCH v2 2/4] x86/bus_lock: Add support for AMD

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Message-ID: <20240712093943.1288-3-ravi.bangoria@amd.com>
Date: Fri, 12 Jul 2024 09:39:41 +0000
From: Ravi Bangoria <ravi.bangoria@....com>
To: <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <seanjc@...gle.com>, <pbonzini@...hat.com>,
	<thomas.lendacky@....com>
CC: <ravi.bangoria@....com>, <hpa@...or.com>, <rmk+kernel@...linux.org.uk>,
	<peterz@...radead.org>, <james.morse@....com>, <lukas.bulwahn@...il.com>,
	<arjan@...ux.intel.com>, <j.granados@...sung.com>, <sibs@...natelecom.cn>,
	<nik.borisov@...e.com>, <michael.roth@....com>, <nikunj.dadhania@....com>,
	<babu.moger@....com>, <x86@...nel.org>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <santosh.shukla@....com>,
	<ananth.narayan@....com>, <sandipan.das@....com>, <manali.shukla@....com>,
	<jmattson@...gle.com>
Subject: [PATCH v2 2/4] x86/bus_lock: Add support for AMD

Upcoming AMD uarch will support Bus Lock Detect (called Bus Lock Trap
in AMD docs). Add support for the same in Linux. Bus Lock Detect is
enumerated with cpuid 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@....com>
---
 arch/x86/kernel/cpu/common.c | 2 ++
 arch/x86/kernel/cpu/intel.c  | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d4e539d4e158..a37670e1ab4d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/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);
 
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 8a483f4ad026..799f18545c6e 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/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);
 }
-- 
2.34.1