[lkml]   [2009]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods
Linus Torvalds wrote:
> On Mon, 15 Jun 2009, Ingo Molnar wrote:
>> A simple cr2 corruption would explain all those cc1 SIGSEGVs and
>> other user-space crashes i saw, with sufficiently intense sampling -
>> easily.
> Note that we could work around the %cr2 issue, since any corruption is
> always nicely "nested" (ie there are never any SMP issues with async
> writes to the register).
> So what we _could_ do is to have a magic value for %cr2, along with a "NMI
> sequence count", and if we see that value, we just return (without doing
> anything) from the page fault handler.

Wouldn't it be simpler to just require the NMI handler to save and
restore %cr2 around any potentially faulting references?


 \ /
  Last update: 2009-06-15 20:45    [from the cache]
©2003-2014 Jasper Spaans. hosted at Digital Ocean