Messages in this thread | | | Subject | Re: [RFC] arm64: mm: update max_pfn after memory hotplug | From | David Hildenbrand <> | Date | Wed, 29 Sep 2021 12:29:32 +0200 |
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On 29.09.21 12:10, Will Deacon wrote: > On Thu, Sep 23, 2021 at 03:54:48PM -0700, Chris Goldsworthy wrote: >> From: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com> >> >> 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. >> >> Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com> >> Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com> >> --- >> 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; >> + } > > We use 'max_pfn' as part of the argument to set_max_mapnr(). Does that need > updating as well? > > Do we have sufficient locking to ensure nobody is looking at max_pfn or > max_low_pfn while we update them?
Only the write side is protected by memory hotplug locking. The read side is lockless -- just like all of the other pfn_to_online_page() machinery.
> > Will >
-- Thanks,
David / dhildenb
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