Re: [PATCH 4/5] x86/kernel: Provide a means to disable TSC ART

From: Mike Travis
Date: Wed Oct 04 2017 - 10:15:23 EST

On 10/4/2017 2:27 AM, Peter Zijlstra wrote:
On Mon, Oct 02, 2017 at 10:12:18AM -0500, mike.travis@xxxxxxx wrote:
static void detect_art(void)
unsigned int unused[2];
- if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
+ if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF || tsc_art_disabled)
/* Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required */

So why can't we use is_uv_system() here an for the tsc_adjust thing?

I could. I just thought that there may be future system arches that
need the same facility?

Also (and I hate the name) tsc_multi_sync_resets is the reason you
cannot use ART, I don't think it makes sense to introduce yet another

Okay. I wasn't sure if there might be different causes for wanting one
condition over the other. So does this mean change this later test to
use is_uv_system() or tsc_multi_sync_resets?