On 04/09/2018 06:12 PM, kernel test robot wrote: > +-----------------------------------------------------------------------+------------+------------+------------+------------+ > | | > 64c8075940 | e71e836f46 | 0564258fb2 | 87e1e2f51c | > +-----------------------------------------------------------------------+------------+------------+------------+------------+ > | boot_successes | 35 > | 0 | 19 | 11 | > | boot_failures | 0 > | 26 | | | > | WARNING:at_arch/x86/include/asm/pgtable.h:#__change_page_attr_set_clr | 0 > | 26 | | | > | RIP:__change_page_attr_set_clr | 0 > | 26 | | | > +-----------------------------------------------------------------------+------------+------------+------------+------------+
LKP folks, does this mean that the system didn't boot in all the places that we saw this warning? Or does this just say that it *had* the warning 26 times? I looked into this a bit. This LKP report points the finger at this commit which trips over a new debugging WARN_ON() I added: [patch 06/11] x86/mm: Remove extra filtering in pageattr code It's because set_memory_nx() encounters the (unsupported) _PAGE_GLOBAL bit while clearing _PAGE_NX. I never saw this in testing because this patch: [PATCH 10/11] x86/pti: never implicitly clear _PAGE_GLOBAL for kernel image explicitly clears out _PAGE_GLOBAL long before the set_memory_nx() call. So I *think* this is a transient issue resulting in bad ordering of the _PAGE_GLOBAL patch set. I believe it is harmless. If anyone is encountering real issues, please speak up.
