From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request
 at 0000a7cf
Date: Thu, 09 Mar 2017 23:11:17 +0100
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References: <58C152F1.9090004@iogearbox.net> <alpine.DEB.2.20.1703091409080.3521@nanos> <58C157E6.1010909@iogearbox.net> <alpine.DEB.2.20.1703091547460.3521@nanos> <58C19607.6000605@iogearbox.net> <CA+55aFyxM--wyvxXGhBOqdJHcdC_kKvGYpv-C5SpYvRNkbEmGw@mail.gmail.com> <CA+55aFyu-LHqMaZBaa7VNamxhUR99F4Xr+nL9esLDUBhotopVg@mail.gmail.com> <58C19F67.3040509@iogearbox.net> <58C1C9DC.7070509@iogearbox.net> <20170309215547.jmdzznlkzaxwu2pf@pd.tnic> <20170309220732.ufqoqlawktsi2gao@pd.tnic>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, Peter Anvin <hpa@zytor.com>,
        Fengguang Wu <fengguang.wu@intel.com>,
        Network Development <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, LKP <lkp@01.org>,
        ast@fb.com, the arch/x86 maintainers <x86@kernel.org>,
        "David S. Miller" <davem@davemloft.net>
To: Borislav Petkov <bp@suse.de>
Return-path: <linux-kernel-owner@vger.kernel.org>
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List-Id: netdev.vger.kernel.org

On 03/09/2017 11:07 PM, Borislav Petkov wrote:
> On Thu, Mar 09, 2017 at 10:55:47PM +0100, Borislav Petkov wrote:
>> Can you make that:
>>
>> 	setup_clear_cpu_cap(X86_FEATURE_PGE);
>>
>> and see if it fixes your issue?
>
> Hmm, in reading the thread a bit more, that might not work. If I see it
> correctly, lguest does
>
>   clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
>
> after the alternatives have run and static_cpu_has() sites have already
> been patched so clearing that bit won't bring anything.

Yeah, I just tried that out and it had no effect unfortunately, the
static_cpu_has() was still 1.