Re: [PATCH RESEND v2 0/5] Avoid requesting page from DMA zone when no managed pages

Baoquan He
2021-12-13T14:04:02Z

On 12/13/21 at 02:25pm, Borislav Petkov wrote:
> On Tue, Dec 07, 2021 at 11:16:31AM +0800, Baoquan He wrote:
> > > This low 1M lock down is needed because AMD SME encrypts memory making
> > > the old backup region mechanims impossible when switching into kdump
> > > kernel. And Intel engineer mentioned their TDX (Trusted domain extensions)
> > > which is under development in kernel also needs lock down the low 1M.
> > > So we can't simply revert above commits to fix the page allocation
> > > failure from DMA zone as someone suggested.
>
> Did you read
>
> f1d4d47c5851 ("x86/setup: Always reserve the first 1M of RAM")
>
> carefully for a more generically important reason as to why the first 1M
> should not be used?

Apparently I didn't. I slacked off and just grabbed things stored in my
brain. This is the right justification and missed. Thanks for pointing
it out.