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)" <rppt@xxxxxxxxxx>
> >
> >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) <rppt@xxxxxxxxxx>
> >---
> > 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().
> BTW, one question here. How we handle concurrent memblock allocation? If two
> threads find the same available range and do the reservation, it seems to be a
> problem to me. Or I missed something?
memblock allocations end before smp_init(), there is no possible concurrency.
> --
> Wei Yang
> Help you, Help me
--
Sincerely yours,
Mike.
