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

From: Linus Torvalds
Date: Thu Mar 09 2017 - 13:15:43 EST


On Thu, Mar 9, 2017 at 10:10 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> 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