[lkml]   [2019]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC] perf/x86/intel: Disable check_msr for real hw
On 24/06/19 00:40, Jiri Olsa wrote:
> On Fri, Jun 21, 2019 at 10:48:25AM -0700, Andi Kleen wrote:
>> 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
>> Sorry for the late comment. I see this patch has been merged now.
>> Unfortunately I don't think it's a good idea. The problem
>> is that the hypervisor flags are only set for a few hypervisors
>> that Linux knows about. But in practice there are many more
>> Hypervisors around that will not cause these flags to be set.
>> But these are still likely to miss MSRs.
>> The other hypervisors are relatively obscure, but eventually
>> someone will hit problems.
> any idea if there's any other flag/way we could use to detect those?

There's no silver bullet, the best is boot_cpu_has(X86_FEATURE_HYPERVISOR).


 \ /
  Last update: 2019-06-24 10:07    [W:0.065 / U:2.744 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site