# arm64 physmap (was Re: \[kernel-hardening\] \[PATCH 4/6\] Protectable Memory)

- From: Kees Cook \<hidden\>
- Date: 2018-02-14 19:35:54 
- List: linux-security-module
- Page: https://ratatoskr.run/linux-security-module/2018/02/5197651
- Thread: https://ratatoskr.run/linux-security-module/2018/01/5184248/t.md

```text
On Wed, Feb 14, 2018 at 11:29 AM, Kees Cook [ref] wrote:
> Why does using finer granularity on the physmap degrade performance? I
> assume TLB pressure, but what is heavily using that area? (I must not
> be understanding what physmap actually gets used for -- I thought it
> was just a convenience to have a 1:1 virt/phys map for some lookups?)

Jann has sorted me out: it's that physmap isn't an _alias_ for the
buddy allocator memory areas; it's used directly.

-Kees

-- 
Kees Cook
Pixel Security
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