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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: ebb1064e7c ("x86/traps: Handle #DB for bus lock")
Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20220802033206.21333-1-chenyi.qiang@intel.com
This commit is contained in:
Chenyi Qiang 2022-08-02 11:32:06 +08:00 committed by Ingo Molnar
parent 9de1f9c8ca
commit ffa6482e46
1 changed files with 14 additions and 13 deletions
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23
arch/x86/kernel/cpu/intel.c
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@ -1216,22 +1216,23 @@ static void bus_lock_init(void)
{
u64 val;
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) {
/*
* 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)
return;
/*
* Enable #DB for bus lock. All bus locks are handled in #DB except
* split locks are handled in #AC in the fatal case.
*/
rdmsrl(MSR_IA32_DEBUGCTLMSR, val);
val &= ~DEBUGCTLMSR_BUS_LOCK_DETECT;
} else {
val |= DEBUGCTLMSR_BUS_LOCK_DETECT;
}
wrmsrl(MSR_IA32_DEBUGCTLMSR, val);
}