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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 9 Mar 2017 10:15:22 -0800
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Subject: Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request
 at 0000a7cf
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>, Laura Abbott <labbott@redhat.com>,
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        Network Development <netdev@vger.kernel.org>,
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On Thu, Mar 9, 2017 at 10:10 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Very odd. We should always have PGE (0x0080) set in cr4 (if the CPU
> supports it).

Daniel, do you see the code in probe_page_size_mask() triggering?

        /* Enable PGE if available */
        if (boot_cpu_has(X86_FEATURE_PGE)) {
                cr4_set_bits_and_update_boot(X86_CR4_PGE);
                __supported_pte_mask |= _PAGE_GLOBAL;
        } else
                __supported_pte_mask &= ~_PAGE_GLOBAL;

but maybe there's something wrong with the percpu cr4 caching?

               Linus