netdev - Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request at 0000a7cf

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Date:   Thu, 09 Mar 2017 23:11:17 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Borislav Petkov <bp@...e.de>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Ingo Molnar <mingo@...nel.org>, Peter Anvin <hpa@...or.com>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>,
        ast@...com, the arch/x86 maintainers <x86@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request
 at 0000a7cf

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.