Commit 4f38b7f4 authored Aug 02, 2022 by Chenyi Qiang Committed by Aichun Shi Nov 03, 2022

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

mainline inclusion
from mainline-v6.0-rc1
commit ffa6482e
category: feature
feature: KVM Bus Lock Debug Exception
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5RHW7
CVE: N/A
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/


commit/?id=ffa6482e

Intel-SIG: commit ffa6482e ("x86/bus_lock: Don't assume the init value of DEBUGCTLMSR.BUS_LOCK_DETECT to be zero")

-------------------------------------

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: 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


Signed-off-by: Aichun Shi <aichun.shi@intel.com>

parent b9ddddea

arch/x86/kernel/cpu/intel.c

+14 −13

Original line number	Diff line number	Diff line
		@@ -1150,22 +1150,23 @@ 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);
		}