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

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Date:   Thu, 9 Mar 2017 14:10:46 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Daniel Borkmann <daniel@...earbox.net>
cc:     Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        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 Thu, 9 Mar 2017, Daniel Borkmann wrote:
> With regard to CPA_FLUSHTLB that Linus mentioned, when I investigated
> code paths in change_page_attr_set_clr(), I did see that CPA_FLUSHTLB
> was set each time we switched attrs and a cpa_flush_range() was
> performed (with the correct number of pages and cache set to 0). That
> would be a __flush_tlb_all() eventually.
> 
> Hmm, it indeed might seem likely that this could be an emulation bug.

Which variant of __flush_tlb_all() is used when the test fails?

Check for the following flags in /proc/cpuinfo: pge invpcid

Thanks,

	tglx