linux-kernel - Re: [PATCH 01/19] x86, mpx, xsave: fix up bad get_xsave

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Message-ID: <alpine.DEB.2.11.1505182110450.4225@nanos>
Date:	Mon, 18 May 2015 21:34:32 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Hansen <dave@...1.net>
cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	dave.hansen@...ux.intel.com
Subject: Re: [PATCH 01/19] x86, mpx, xsave: fix up bad get_xsave_addr()
 assumptions

On Fri, 8 May 2015, Dave Hansen wrote:
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> get_xsave_addr() assumes that if an xsave bit is present in the
> hardware (pcntxt_mask) that it is present in a given xsave
> buffer.  Due to an bug in the xsave code on all of the systems
> that have MPX (and thus all the users of this code), that has
> been a true assumption.
> 
> But, the bug is getting fixed, so our assumption is not going
> to hold any more.
> 
> It's quite possible (and normal) for an enabled state to be
> present on 'pcntxt_mask', but *not* in 'xstate_bv'.  We need
> to consult 'xstate_bv'.
> 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
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