X86_FEATURE_HYPERVISOR and X86_FEATURE_BUS_LOCK_DETECT are always enumerated in a TDX guest because the corresponding CPUID values are fixed to 1 by the TDX module. Similar to a normal guest, a TDX guest never enumerates X86_FEATURE_SPLIT_LOCK_DETECT. When "split_lock_detect=off", the TDX guest kernel log shows: x86/split lock detection: disabled and with other settings, it shows: x86/split lock detection: #DB: ... However, if the host enables split lock detection, a TDX guest receives #AC regardless of its own "split_lock_detect" configuration. The actual behavior does not match what the kernel log claims. Call out the possible #AC behavior on TDX and highlight that this behavior depends on the host's enabling of split lock detection. Signed-off-by: Xiaoyao Li --- arch/x86/kernel/cpu/bus_lock.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/cpu/bus_lock.c b/arch/x86/kernel/cpu/bus_lock.c index f278e4ea3dd4..18695214d214 100644 --- a/arch/x86/kernel/cpu/bus_lock.c +++ b/arch/x86/kernel/cpu/bus_lock.c @@ -437,6 +437,9 @@ static void sld_state_show(void) pr_info("#DB: setting system wide bus lock rate limit to %u/sec\n", bld_ratelimit.burst); break; } + + if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) + pr_info("tdx: #AC depends on host configuration: crashing the kernel on kernel split_locks and sending SIGBUS on user-space split_locks\n"); } void __init sld_setup(struct cpuinfo_x86 *c) -- 2.43.0