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Date: Fri, 16 May 2014 09:54:40 -0700
From: Dave Hansen <dave.hansen@intel.com>
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To: "H. Peter Anvin" <hpa@zytor.com>, David Vrabel <david.vrabel@citrix.com>,
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Subject: Re: [PATCH] x86: skip check for spurious faults for non-present faults
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On 05/15/2014 02:20 PM, H. Peter Anvin wrote:
> I'm trying to wrap my head around any forward compatibility
> concerns... if we misidentify a fault as spurious that would be bad.

FWIW, I did go through the bullets in the SDM's "4.10.4.3 Optional
Invalidation".  The only condition not covered by this patch is the one
that talks about "CR4.SMEP = 0...".

But, I don't know of any case where we take a userspace page and make it
supervisor-only, so I don't think this is possible now.