perf/x86: Avoid touching LBR_TOS MSR for Arch LBR

The Architecture LBR does not have MSR_LBR_TOS (0x000001c9).
In a guest that should support Architecture LBR, check_msr()
will be a non-related check for the architecture MSR 0x0
(IA32_P5_MC_ADDR) that is also not supported by KVM.

The failure will cause x86_pmu.lbr_nr = 0, thereby preventing
the initialization of the guest Arch LBR. Fix it by avoiding
this extraneous check in intel_pmu_init() for Arch LBR.

Fixes: 47125db27e47 ("perf/x86/intel/lbr: Support Architectural LBR")
Signed-off-by: Like Xu <>
[peterz: simpler still]
Signed-off-by: Peter Zijlstra (Intel) <>
1 file changed