linux-kernel - Re: [PATCH] x86: skip check for spurious faults for non-present faults

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Message-ID: <537642D0.60105@intel.com>
Date:	Fri, 16 May 2014 09:54:40 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	David Vrabel <david.vrabel@...rix.com>,
	linux-kernel@...r.kernel.org
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Subject: Re: [PATCH] x86: skip check for spurious faults for non-present faults

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.
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