Messages in this thread | | | Date | Fri, 15 Jun 2012 14:52:40 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge |
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On Fri, Jun 15, 2012 at 02:42:41PM +0200, Peter Zijlstra wrote: > On Fri, 2012-06-15 at 14:37 +0200, Borislav Petkov wrote: > > This is a minimal fix which we'd like to see in stable too thus the > > more-or-less arbitrary decision to allow system-wide reloading only on > > the BSP: > > > > $ echo 1 > /sys/devices/system/cpu/cpu0/microcode/reload > > ... > > > > and disable the interface on the other cores: > > > > $ echo 1 > /sys/devices/system/cpu/cpu23/microcode/reload > > -bash: echo: write error: Invalid argument > > One could allow the reload from all cpus and simply do all cpus, but I > guess the rationale for not doing that and restricting it to cpu0 is to > avoid the O(n^2) thing in case userspace issues a reload on all cpus?
That's a good point.
Actually, the BSP thing was more-or-less an arbitrary deal. What we want as an endresult is to do:
$ echo 1 > /sys/devices/system/cpu/microcode/reload
(notice this is in the toplevel "cpu" directory in sysfs)
and do the system-wide reload there.
Obviously, this needs a couple of more patches and we wanted to have a simplest stable fix first.
> If so it would be good to mention in the Changelog so people see its not > a 'random' choice.
Yes, will do, thanks!
-- Regards/Gruss, Boris.
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