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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YbdJ00wRFvi0aqze@zn.tnic>
Date:   Mon, 13 Dec 2021 14:25:39 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org, hch@....de,
        robin.murphy@....com, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com, vbabka@...e.cz,
        m.szyprowski@...sung.com, John.p.donnelly@...cle.com,
        kexec@...ts.infradead.org, rppt@...ux.ibm.com
Subject: Re: [PATCH RESEND v2 0/5] Avoid requesting page from DMA zone when
 no managed pages

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?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette