Message-ID: <5356FE03.5070000@linux.intel.com>
Date: Tue, 22 Apr 2014 16:40:51 -0700
From: "H. Peter Anvin" <hpa@linux.intel.com>
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To: Andi Kleen <andi@firstfloor.org>, "H. Peter Anvin" <hpa@zytor.com>
CC: Brian Gerst <brgerst@gmail.com>, Andrew Lutomirski <amluto@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Borislav Petkov <bp@alien8.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Alexander van Heukelum <heukelum@fastmail.fm>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Arjan van de Ven <arjan.van.de.ven@intel.com>,
        Alexandre Julliard <julliard@winehq.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*
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On 04/22/2014 04:39 PM, Andi Kleen wrote:
>> That simply will not work if you can take a #GP due to the "safe" MSR
>> functions from NMI and #MC context, which would be my main concern.
> 
> At some point the IST entry functions subtracted 1K while the
> handler ran to handle simple nesting cases.
> 
> Not sure that code is still there.

Doesn't help if you take an NMI on the first instruction of the #GP handler.

	-hpa


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