On 03/24/2017 at 08:04 PM, Kirill A. Shutemov wrote: > On Mon, Mar 20, 2017 at 02:11:31PM +0800, Xunlei Pang wrote: >> I found that the kdump is broken on linux-4.11.0-rc2+ > That's actually tip tree or linux-next. The problematic change is not in > Linus' tree. > >> , probably >> due to the 5level-paging feature that "#define p4d_present(p4d) 1", >> as a result in ident_p4d_init(), it will go into ident_pud_init() >> directly without allocating the new pud. >> >> Looks like this patch can make it work again. > Okay, that's bisectability issue. Uncovered by splitting my patchset into > parts. > > Could you check if applying "Part 2" of 5-level paging changes[1] would > help you? I confirmed that it works after applying your following patches: x86: Convert the rest of the code to support p4d_t x86/xen: Change __xen_pgd_walk() and xen_cleanmfnmap() to support p4d x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h> x86/mm/pat: Add 5-level paging support x86/efi: Add 5-level paging support x86/kexec: Add 5-level paging support Regards, Xunlei > > Making the code work with both <asm-generic/5level-fixup.h> and > <asm-generic/pgtable-nop4d.h> would make it even uglier. Not sure if it > makes sense to address it on its own if second part fixes the situation. > > [1] http://lkml.kernel.org/r/20170317185515.8636-1-kirill.shutemov at linux.intel.com >
