Commit ffa6482e authored by Chenyi Qiang's avatar Chenyi Qiang Committed by Ingo Molnar
Browse files

x86/bus_lock: Don't assume the init value of DEBUGCTLMSR.BUS_LOCK_DETECT to be zero 



It's possible that this kernel has been kexec'd from a kernel that
enabled bus lock detection, or (hypothetically) BIOS/firmware has set
DEBUGCTLMSR_BUS_LOCK_DETECT.

Disable bus lock detection explicitly if not wanted.

Fixes: ebb1064e ("x86/traps: Handle #DB for bus lock")
Signed-off-by: default avatarChenyi Qiang <chenyi.qiang@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarTony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20220802033206.21333-1-chenyi.qiang@intel.com
parent 9de1f9c8

arch/x86/kernel/cpu/intel.c

+14 −13
Original line number Diff line number Diff line
@@ -1216,22 +1216,23 @@ static void bus_lock_init(void) 
{

	u64 val;



	/*

	 * Warn and fatal are handled by #AC for split lock if #AC for

	 * split lock is supported.

	 */

	if (!boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT) ||

	    (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT) &&

	    (sld_state == sld_warn || sld_state == sld_fatal)) ||

	    sld_state == sld_off)

	if (!boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT))

		return;



	rdmsrl(MSR_IA32_DEBUGCTLMSR, val);



	if ((boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT) &&

	    (sld_state == sld_warn || sld_state == sld_fatal)) ||

	    sld_state == sld_off) {

		/*

	 * Enable #DB for bus lock. All bus locks are handled in #DB except

	 * split locks are handled in #AC in the fatal case.

		 * Warn and fatal are handled by #AC for split lock if #AC for

		 * split lock is supported.

		 */

	rdmsrl(MSR_IA32_DEBUGCTLMSR, val);

		val &= ~DEBUGCTLMSR_BUS_LOCK_DETECT;

	} else {

		val |= DEBUGCTLMSR_BUS_LOCK_DETECT;

	}



	wrmsrl(MSR_IA32_DEBUGCTLMSR, val);

}