Re: [GIT PULL] x86/mm changes for v4.21

[Linus Torvalds]

On Thu, Feb 7, 2019 at 1:24 PM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>
> How bad would it be to set CR0.CD while fiddling with the page tables rather than masking the address?

I would suggest against it. When you disable caching, things don't
just go "slightly slower". Everything comes to a screeching halt, with
instruction fetch etc becoming a serious problem.

So disabling caching for a few instructions in a very simple asm
snippet might be reasonable (particularly since you could pre-fetch
the cache and just rely on CR0.CD not fetching *new* lines). But doing
it in C code that might have things like tracing enabled etc? I'd be
very very leery.

                 Linus