On 02.06.21 13:10, Max Gurtovoy wrote:
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.
Just some high-level questions:
A CMB is just a PCI BAR used for communicating with the device, to be
mapped into physical address space, right? I assume the relevant hotplug
code is:
drivers/pci/p2pdma.c: addr = devm_memremap_pages(&pdev->dev, pgmap);
correct?
Having a BAR span such weird sizes will most probably never be fully
supported. But if sub-sections work for you, great.
--
Thanks,
David / dhildenb
