hi Kirill, As Mike reported it below, your 5-level paging related upstream commit 83e3c48729d9 and all its followup fixes: 83e3c48729d9: mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y 629a359bdb0e: mm/sparsemem: Fix ARM64 boot crash when CONFIG_SPARSEMEM_EXTREME=y d09cfbbfa0f7: mm/sparse.c: wrong allocation for mem_section ... still breaks kexec - and that now regresses -stable as well. Given that 5-level paging now syntactically depends on having this commit, if we fully revert this then we'll have to disable 5-level paging as well. Thanks, Ingo * Mike Galbraith <efault@xxxxxx> wrote: > On Fri, 2017-12-22 at 09:45 +0100, Greg Kroah-Hartman wrote: > > 4.14-stable review patch. If anyone has any objections, please let me know. > > FYI, this broke kdump, or rather the makedumpfile part thereof. > Forward looking wreckage is par for the kdump course, but... > > > ------------------ > > > > From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > > > commit 83e3c48729d9ebb7af5a31a504f3fd6aff0348c4 upstream. > > > > Size of the mem_section[] array depends on the size of the physical address space. > > > > In preparation for boot-time switching between paging modes on x86-64 > > we need to make the allocation of mem_section[] dynamic, because otherwise > > we waste a lot of RAM: with CONFIG_NODE_SHIFT=10, mem_section[] size is 32kB > > for 4-level paging and 2MB for 5-level paging mode. > > > > The patch allocates the array on the first call to sparse_memory_present_with_active_regions(). > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > > Cc: Borislav Petkov <bp@xxxxxxx> > > Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: linux-mm@xxxxxxxxx > > Link: http://lkml.kernel.org/r/20170929140821.37654-2-kirill.shutemov@xxxxxxxxxxxxxxx > > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > > > --- > > include/linux/mmzone.h | 6 +++++- > > mm/page_alloc.c | 10 ++++++++++ > > mm/sparse.c | 17 +++++++++++------ > > 3 files changed, 26 insertions(+), 7 deletions(-) > > > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -1152,13 +1152,17 @@ struct mem_section { > > #define SECTION_ROOT_MASK (SECTIONS_PER_ROOT - 1) > > > > #ifdef CONFIG_SPARSEMEM_EXTREME > > -extern struct mem_section *mem_section[NR_SECTION_ROOTS]; > > +extern struct mem_section **mem_section; > > #else > > extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; > > #endif > > > > static inline struct mem_section *__nr_to_section(unsigned long nr) > > { > > +#ifdef CONFIG_SPARSEMEM_EXTREME > > + if (!mem_section) > > + return NULL; > > +#endif > > if (!mem_section[SECTION_NR_TO_ROOT(nr)]) > > return NULL; > > return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK]; > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -5651,6 +5651,16 @@ void __init sparse_memory_present_with_a > > unsigned long start_pfn, end_pfn; > > int i, this_nid; > > > > +#ifdef CONFIG_SPARSEMEM_EXTREME > > + if (!mem_section) { > > + unsigned long size, align; > > + > > + size = sizeof(struct mem_section) * NR_SECTION_ROOTS; > > + align = 1 << (INTERNODE_CACHE_SHIFT); > > + mem_section = memblock_virt_alloc(size, align); > > + } > > +#endif > > + > > for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid) > > memory_present(this_nid, start_pfn, end_pfn); > > } > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -23,8 +23,7 @@ > > * 1) mem_section - memory sections, mem_map's for valid memory > > */ > > #ifdef CONFIG_SPARSEMEM_EXTREME > > -struct mem_section *mem_section[NR_SECTION_ROOTS] > > - ____cacheline_internodealigned_in_smp; > > +struct mem_section **mem_section; > > #else > > struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT] > > ____cacheline_internodealigned_in_smp; > > @@ -101,7 +100,7 @@ static inline int sparse_index_init(unsi > > int __section_nr(struct mem_section* ms) > > { > > unsigned long root_nr; > > - struct mem_section* root; > > + struct mem_section *root = NULL; > > > > for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) { > > root = __nr_to_section(root_nr * SECTIONS_PER_ROOT); > > @@ -112,7 +111,7 @@ int __section_nr(struct mem_section* ms) > > break; > > } > > > > - VM_BUG_ON(root_nr == NR_SECTION_ROOTS); > > + VM_BUG_ON(!root); > > > > return (root_nr * SECTIONS_PER_ROOT) + (ms - root); > > } > > @@ -330,11 +329,17 @@ again: > > static void __init check_usemap_section_nr(int nid, unsigned long *usemap) > > { > > unsigned long usemap_snr, pgdat_snr; > > - static unsigned long old_usemap_snr = NR_MEM_SECTIONS; > > - static unsigned long old_pgdat_snr = NR_MEM_SECTIONS; > > + static unsigned long old_usemap_snr; > > + static unsigned long old_pgdat_snr; > > struct pglist_data *pgdat = NODE_DATA(nid); > > int usemap_nid; > > > > + /* First call */ > > + if (!old_usemap_snr) { > > + old_usemap_snr = NR_MEM_SECTIONS; > > + old_pgdat_snr = NR_MEM_SECTIONS; > > + } > > + > > usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT); > > pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT); > > if (usemap_snr == pgdat_snr) > > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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