On Fri, Jun 14, 2019 at 01:28:53PM +0200, Jiri Olsa wrote:
> hi,
> the HPE server can do POST tracing and have enabled LBR
> tracing during the boot, which makes check_msr fail falsly.
>
> It looks like check_msr code was added only to check on guests
> MSR access, would it be then ok to disable check_msr for real
> hardware? (as in patch below)
>
> We could also check if LBR tracing is enabled and make
> appropriate checks, but this change is simpler ;-)
>
> ideas? thanks,
> jirka
>
>
> ---
> arch/x86/events/intel/core.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 71001f005bfe..1194ae7e1992 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -20,6 +20,7 @@
> #include <asm/intel-family.h>
> #include <asm/apic.h>
> #include <asm/cpu_device_id.h>
> +#include <asm/hypervisor.h>
>
> #include "../perf_event.h"
>
> @@ -4050,6 +4051,13 @@ static bool check_msr(unsigned long msr, u64 mask)
> {
> u64 val_old, val_new, val_tmp;
>
> + /*
> + * Disable the check for real HW, so we don't
> + * mess up with potentionaly enabled regs.
> + */
> + if (hypervisor_is_type(X86_HYPER_NATIVE))
> + return true;
Yeah, I think that works, or !boot_cpu_has(X86_FEATURE_HYPERVISOR).
> /*
> * Read the current value, change it and read it back to see if it
> * matches, this is needed to detect certain hardware emulators
> --
> 2.21.0
>
