On 01.10.21 08:38, Anshuman Khandual wrote:

On 9/29/21 12:21 AM, Chris Goldsworthy wrote:

quoted

From: Sudarshan Rajagopalan <redacted>

After new memory blocks have been hotplugged, max_pfn and max_low_pfn
needs updating to reflect on new PFNs being hot added to system.
Without this patch, debug-related functions that use max_pfn such as
get_max_dump_pfn() or read_page_owner() will not work with any page in
memory that is hot-added after boot.

Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
Signed-off-by: Sudarshan Rajagopalan <redacted>
Signed-off-by: Chris Goldsworthy <redacted>
Acked-by: David Hildenbrand <redacted>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Georgi Djakov <redacted>
---
  arch/arm64/mm/mmu.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index cfd9deb..fd85b51 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c

@@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
  	if (ret)
  		__remove_pgd_mapping(swapper_pg_dir,
  				     __phys_to_virt(start), size);
+	else {
+		max_pfn = PFN_UP(start + size);
+		max_low_pfn = max_pfn;
+	}

Do these variables get updated on *all* platforms that support memory
hotplug via an arch_add_memory() ? If not, dont they all face similar
issues as well ? Why not just update these in generic hotplug instead
, after looking into arch_add_memory() return code.

s390x sets them to the possible maximum (based on the direct mapping 
size) in init code.

Other archs like x86-64 have to update other parameters. So I guess it 
just made sense to let the archs handle updating these 2 variables.

-- 
Thanks,

David / dhildenb


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