Hi all,
In hotplugged memory (from check_pfn_span function):
"
Disallow all operations smaller than a sub-section and only
allow operations smaller than a section for
SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
enforces a larger memory_block_size_bytes() granularity for
memory that will be marked online, so this check should only
fire for direct arch_{add,remove}_memory() users outside of
add_memory_resource()
"
This restriction will disqualify, for example, large NVMe CMBs that might have
non power of 2 number of pages (e.g. 32767 pages of 4KB). For these
devices, the CMB size will be rounded down from 0x7fff000 to 0x7e00000
but it's better than having un-mapped CMB.
If we all agree on the approach, this RFC can assist as-is to these NVMe
devices and other P2PMEM devices in the future and can considered for
the next merge window.
Max Gurtovoy (3):
mm,memory_hotplug: export mhp min alignment
PCI/P2PMEM: introduce pci_p2pdma_align_size API
nvme-pci: align CMB size according to P2PMEM alignment
drivers/nvme/host/pci.c | 7 +++++++
drivers/pci/p2pdma.c | 23 +++++++++++++++++++++++
include/linux/memory_hotplug.h | 5 +++++
include/linux/pci-p2pdma.h | 5 +++++
mm/memory_hotplug.c | 33 +++++++++++++++++++--------------
5 files changed, 59 insertions(+), 14 deletions(-)
--
2.18.1
