From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rik van Riel <riel@surriel.com>
Subject: Re: [PATCH 00/11 v3] x86: load FPU registers on return to userland
Date: Thu, 04 Oct 2018 12:45:08 -0400
Message-ID: <8ea44ae2bb4844df812ea4c6cb0c00ef12708c51.camel@surriel.com>
References: <20181004140547.13014-1-bigeasy@linutronix.de>
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Cc: x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,
        kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Dave Hansen <dave.hansen@linux.intel.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        linux-kernel@vger.kernel.org
Return-path: <linux-kernel-owner@vger.kernel.org>
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On Thu, 2018-10-04 at 16:05 +0200, Sebastian Andrzej Siewior wrote:


> In v3 I dropped that decouple idea. I also learned that the wrpkru
> instruction is not privileged and so caching it in kernel does not
> work.

Wait, so any thread can bypass its memory protection
keys, even if there is a seccomp filter preventing
it from calling the PKRU syscalls?

Is that intended?

Is that simply a hardware limitation, or something
where we can set a flag somewhere to force tasks to
go through the kernel?

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