Messages in this thread | | | From | Wolfgang Walter <> | Subject | Re: Kernel oops with 2.6.26, padlock and ipsec: probably problem with fpu state changes | Date | Sat, 9 Aug 2008 04:43:00 +0200 |
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On Saturday 09 August 2008, Herbert Xu wrote: > On Fri, Aug 08, 2008 at 12:01:15PM -0700, H. Peter Anvin wrote: > > > > It's technically overkill, if (and only if!) these instructions don't > > actually touch the SSE state (most likely they're using the SSE > > pipeline, and need this stuff to deal with power management issues.) > > Yes the PadLock uses the SSE pipeline, but doesn't touch any > of the state. > > > However, overkill is a good way to make sure something is dead. > > Applying the patch will make sure we fix the regression, and we can > > worry about optimizing this further post-2.6.27. > > Do we really need the FPU changes right now? I'd prefer for that > to be backed out until a proper solution is found. Disabling > preemption around crypto is really bad for scheduling latency. >
These FPU changes are already in 2.6.26. Undoing them, would that be accepted for 2.6.26 stable?
Maybe the following solution would be possible: if a processor with padlock is detected the memory for xstate is always allocated when the thread is created instead "lazy"?
Or would it be possible to change __switch_to(): bevor calling __unlazy_fpu() check if xstate is NULL, if yes, clear TS_USEDFPU and math-state?
As I wrote in my other mail: 2.6.26 with the patch seems to perform rather well with ipsec. Network latency and bandwidth seem completely unchanged compared to 2.6.15.13 as far as I can see yet.
But this is of course not a good test for kernel latency itself. As we don't have any destops based on VIA C3 (and these using padlock) I can't really test this (even if I set one up I don't know how it used to feel with 2.6.25 :-) ).
But I doubt that a lot of people use it as a desktop together with a VIA C3 and ipsec. If they would they must see this crash.
Regards, -- Wolfgang Walter Studentenwerk München Anstalt des öffentlichen Rechts Leiter EDV Leopoldstraße 15 80802 München Tel: +49 89 38196-276 Fax: +49 89 38196-144 wolfgang.walter@stwm.de http://www.studentenwerk-muenchen.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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