On 2025/1/3 2:58, Catalin Marinas wrote:
On Fri, Dec 27, 2024 at 01:19:30PM +0530, Anshuman Khandual wrote:
On 12/24/24 19:39, Catalin Marinas wrote:
On Tue, Dec 24, 2024 at 05:32:06PM +0800, Zhenhua Huang wrote:
I have two ideas:
1. Completely disable this PMD mapping optimization since there is no
guarantee we must align 128M memory for hotplug ..
I'd be in favour of this, at least if CONFIG_MEMORY_HOTPLUG is enabled.
I think the only advantage here is that we don't allocate a full 2MB
block for vmemmap when only plugging in a sub-section.
Agreed, that will be the right fix for the problem which can be back ported.
We will have to prevent PMD/PUD/CONT mappings for both linear and as well as
vmemmap for all non-boot memory sections, that can be hot-unplugged.
I haven't read your diffs below yet but why not allow PMD mappings of
the hotplugged memory (not vmemmap)? SUBSECTION_SHIFT is 21, so we can
have 2MB blocks in a 4KB page configuration.
Oh, Understood. We discussed the topic and I shared the same concern,
Anshuman actually preferred to wait for your decision.
See discussion:
https://lore.kernel.org/lkml/3aadda40-c973-4703-8ed8-9cf2d3eb70a0@xxxxxxxxxxx/
I see your favor now and will post V3 based on that.
