Hi Wei, On Mon, Mar 10, 2025 at 09:51:24AM +0000, Wei Yang wrote: > On Sun, Feb 23, 2025 at 12:22:29AM +0000, Wei Yang wrote: > >On Wed, Feb 19, 2025 at 09:24:31AM +0200, Mike Rapoport wrote: > >>Hi, > >> > >>On Tue, Feb 18, 2025 at 03:50:04PM +0000, Wei Yang wrote: > >>> On Thu, Feb 06, 2025 at 03:27:42PM +0200, Mike Rapoport wrote: > >>> >From: "Mike Rapoport (Microsoft)" <[email protected]> > >>> > > >>> >to denote areas that were reserved for kernel use either directly with > >>> >memblock_reserve_kern() or via memblock allocations. > >>> > > >>> >Signed-off-by: Mike Rapoport (Microsoft) <[email protected]> > >>> >--- > >>> > include/linux/memblock.h | 16 +++++++++++++++- > >>> > mm/memblock.c | 32 ++++++++++++++++++++++++-------- > >>> > 2 files changed, 39 insertions(+), 9 deletions(-) > >>> > > >>> >diff --git a/include/linux/memblock.h b/include/linux/memblock.h > >>> >index e79eb6ac516f..65e274550f5d 100644 > >>> >--- a/include/linux/memblock.h > >>> >+++ b/include/linux/memblock.h > >>> >@@ -50,6 +50,7 @@ enum memblock_flags { > >>> > MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct > >>> > mapping */ > >>> > MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver > >>> > */ > >>> > MEMBLOCK_RSRV_NOINIT = 0x10, /* don't initialize struct > >>> > pages */ > >>> >+ MEMBLOCK_RSRV_KERN = 0x20, /* memory reserved for kernel > >>> >use */ > >>> > >>> Above memblock_flags, there are comments on explaining those flags. > >>> > >>> Seems we miss it for MEMBLOCK_RSRV_KERN. > >> > >>Right, thanks! > >> > >>> > > >>> > #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP > >>> >@@ -1459,14 +1460,14 @@ phys_addr_t __init > >>> >memblock_alloc_range_nid(phys_addr_t size, > >>> > again: > >>> > found = memblock_find_in_range_node(size, align, start, end, > >>> > nid, > >>> > flags); > >>> >- if (found && !memblock_reserve(found, size)) > >>> >+ if (found && !__memblock_reserve(found, size, nid, > >>> >MEMBLOCK_RSRV_KERN)) > >>> > >>> Maybe we could use memblock_reserve_kern() directly. If my understanding > >>> is > >>> correct, the reserved region's nid is not used. > >> > >>We use nid of reserved regions in reserve_bootmem_region() (commit > >>61167ad5fecd ("mm: pass nid to reserve_bootmem_region()")) but KHO needs to > >>know the distribution of reserved memory among the nodes before > >>memmap_init_reserved_pages(). > >> > > > >I took another look into this commit. There maybe a very corner case in which > >will leave a reserved region with no nid set. > > > >memmap_init_reserved_pages() > > for_each_mem_region() { > > ... > > memblock_set_node(start, end, &memblock.reserved, nid); > > } > > > >We leverage the iteration here to set nid to all regions in > >memblock.reserved. > >But memblock_set_node() may call memblock_double_array() to expand the array, > >which may get a range before current start. So we would miss to set the > >correct nid to the new reserved region. > > > >I have tried to create a case in memblock test. This would happen when there > >are 126 memblock.reserved regions. And the last region is across the last two > >node. > > > >One way to fix this is compare type->max in memblock_set_node(). Then check > >this return value in memmap_init_reserved_pages(). If we found the size > >changes, repeat the iteration. > > > >But this is a very trivial one, not sure it worth fix. > > > > Hi, Mike > > I have done a user space test which shows we may have a chance to leave a > region with non-nid set. > > Not sure you are ok with my approach of fixing.
Wouldn't it be better to check for a change in reserved.max in memmap_init_reserved_pages()? > -- > Wei Yang > Help you, Help me -- Sincerely yours, Mike.
