linux-kernel - Re: [PATCHv3 2/4] x86/64/mm: Make SPARSEMEM

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: <f93a6e4d-4970-4352-97ff-643d67662c32@intel.com>
Date: Fri, 16 May 2025 07:59:42 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 Jonathan Corbet <corbet@....net>, Andy Lutomirski <luto@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ard Biesheuvel <ardb@...nel.org>,
 Jan Kiszka <jan.kiszka@...mens.com>, Kieran Bingham <kbingham@...nel.org>,
 Michael Roth <michael.roth@....com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Brijesh Singh <brijesh.singh@....com>, Sandipan Das <sandipan.das@....com>,
 Juergen Gross <jgross@...e.com>, Tom Lendacky <thomas.lendacky@....com>,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-efi@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv3 2/4] x86/64/mm: Make SPARSEMEM_VMEMMAP the only memory
 model

On 5/16/25 06:45, Ingo Molnar wrote:
> Isn't it the other way around? MAX_PHYS{MEM,ADDR}_BITS are now *always* 
> dynamic, their value depending on whether LA57 is available and used.

MAX_PHYS{MEM,ADDR}_BITS were always intended to be the compile-time
maximums on the architecture. They're static on every architecture
except x86 and some arm64 configs (who probably copied x86).

That's why having them be dynamic broke non-vmemmap sparsemem.

But we also seems to have defined MAXMEM to derive from MAX_PHYSMEM_BITS
and MAXMEM cascades into a bunch of other stuff, including KASAN. So we
can't just make them static again, I guess.

The only option would be to make them static when using non-vmemmap
sparsemem. But that's new-ish, and probably won't get any testing.

I guess there's not much we can do about it.