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Date: Tue, 12 Dec 2017 21:37:52 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave.hansen@intel.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
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Subject: Re: [patch 13/16] x86/ldt: Introduce LDT write fault handler
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On Tue, 12 Dec 2017, Dave Hansen wrote:

> On 12/12/2017 11:21 AM, Thomas Gleixner wrote:
> > The only critical interaction is the return to user path (user CS/SS) and
> > we made sure with the LAR touching that these are precached in the CPU
> > before we go into fragile exit code.
> 
> How do we make sure that it _stays_ cached?
> 
> Surely there is weird stuff like WBINVD or SMI's that can come at very
> inconvenient times and wipe it out of the cache.

This does not look like cache in the sense of memory cache. It seems to be
CPU internal state and I just stuffed WBINVD and alternatively CLFLUSH'ed
the entries after the 'touch' via LAR. Still works.

Thanks,

	tglx