Messages in this thread | | | Date | Wed, 13 Jun 2012 18:11:39 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge |
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On Wed, Jun 13, 2012 at 09:36:49AM -0300, Henrique de Moraes Holschuh wrote: > Yes, please. I suggest we use core 0 for that. Using my Debian > maintainer hat, I'd rather you got rid of the sysfs entries for every > other core while at it, as it will make our life a lot simpler, > distro-side.
Wouldn't we have some sort of ABI breakage if I remove the sysfs files? Instead, I was thinking of having the rest of the files not on the BSP return -EINVAL and only the BSP reload ucode on the whole system.
> This is still not the proper fix, which would be to add a new sysfs node > to access the proper update-every-core functionality, but it is a damn > good start in the right direction and required to make it safe without > ripping out the old ABI entirely without a deprecation period.
Yes, I'd like to have the system-wide sysfs node somewhere under /sys/devices/system/cpu/microcode/ but we'll see how that goes.
> Since Intel processors don't want the per-core behaviour either, you > could fix it in the microcode core itself...
Yes.
> Ok. Please CC me in the patches, if the new ABI arrives in time, I'll > even be able to get it supported on the next Debian stable (and push > to get this stuff backported to the kernel 3.2 which we will ship, > I consider this an important bug-fix to a pontentially very serious > issue. We have *zero* chance of finding out what's wrong if an users' > system start getting subtly crazy because it is running with skewed > microcode among cores.
Ok, will do.
Btw, I have to think about whether we really want to backport this to stable since it is not a regression fix but functionality change which kinda fixes a some sort of bug. Hmm, the stable rules are kinda blurry here. I could write a minimal fix with stable in mind though... we'll see.
hpa, what is our take here, should we backport a minimal change disabling reloading of ucode per-cpu for stable? It is the wrong thing to do anyway.
-- Regards/Gruss, Boris.
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