Re: [PATCH] perf/x86/intel: Disable check_msr for real hw
From: Vaden, Tom (HPE Server OS Architecture)
Date: Sun Jun 16 2019 - 17:01:27 EST
On 6/16/19 10:13 AM, Jiri Olsa wrote:
> On Fri, Jun 14, 2019 at 09:45:21AM -0400, Liang, Kan wrote:
>> On 6/14/2019 7:28 AM, Jiri Olsa wrote:
>>> 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)
>> Yes, the check_msr patch was to fix a bug report in guest.
>> I didn't get similar bug report for real hardware.
>> I think it should be OK to disable it for real hardware.
> thanks for confirmation, attaching the full patch
> Tom Vaden reported false failure of check_msr function, because
> some servers can do POST tracing and enable LBR tracing during
> the boot.
> Kan confirmed that check_msr patch was to fix a bug report in
> guest, so it's ok to disable it for real HW.
> Cc: Kan Liang <kan.liang@xxxxxxxxx>
> Reported-by: Tom Vaden <tom.vaden@xxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Thanks for handling the patch.
Acked-by: Tom Vaden <tom.vaden@xxxxxxx>
> 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;
> * Read the current value, change it and read it back to see if it
> * matches, this is needed to detect certain hardware emulators