linux-kernel - Re: [PATCH v9 10/13] cxl: Enable AMD Zen5 address translation using ACPI PRMT

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: <CAMj1kXFhBdCPW_+xPR-TmU4M46Jr6DGwtjUtjDQ0EbgPGmL7vQ@mail.gmail.com>
Date: Wed, 14 Jan 2026 16:21:03 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Robert Richter <rrichter@....com>
Cc: Peter Zijlstra <peterz@...radead.org>, Alison Schofield <alison.schofield@...el.com>, 
	Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, 
	Dan Williams <dan.j.williams@...el.com>, Jonathan Cameron <jonathan.cameron@...wei.com>, 
	Dave Jiang <dave.jiang@...el.com>, Davidlohr Bueso <dave@...olabs.net>, linux-cxl@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Gregory Price <gourry@...rry.net>, 
	"Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>, Terry Bowman <terry.bowman@....com>, 
	Joshua Hahn <joshua.hahnjy@...il.com>
Subject: Re: [PATCH v9 10/13] cxl: Enable AMD Zen5 address translation using
 ACPI PRMT

On Wed, 14 Jan 2026 at 15:00, Robert Richter <rrichter@....com> wrote:
>
> On Wed, Jan 14, 2026 at 08:47:22AM +0100, Ard Biesheuvel wrote:
> > (cc Peter)
> >
> > On Sat, 10 Jan 2026 at 12:46, Robert Richter <rrichter@....com> wrote:
> > >
> > > Add AMD Zen5 support for address translation.
> > >
> > ...
> > > Do the following to implement AMD Zen5 address translation:
> > >
> > > Introduce a new file core/atl.c to handle ACPI PRM specific address
> > > translation code. Naming is loosely related to the kernel's AMD
> > > Address Translation Library (CONFIG_AMD_ATL) but implementation does
> > > not depend on it, nor it is vendor specific. Use Kbuild and Kconfig
> > > options respectively to enable the code depending on architecture and
> > > platform options.
> > >
> > > AMD Zen5 systems support the ACPI PRM CXL Address Translation firmware
> > > call (see ACPI v6.5 Porting Guide, Address Translation - CXL DPA to
> > > System Physical Address). Firmware enables the PRM handler if the
> > > platform has address translation implemented. Check firmware and
> > > kernel support of ACPI PRM using the specific GUID. On success enable
> > > address translation by setting up the earlier introduced root port
> > > callback, see function cxl_prm_setup_translation(). Setup is done in
> > > cxl_setup_prm_address_translation(), it is the only function that
> > > needs to be exported. For low level PRM firmware calls, use the ACPI
> > > framework.
> > >
> >
> > Does the PRM service in question tolerate being invoked unprivileged?
> > The PRM spec requires this, and this is something we may need to
> > enforce at some point.
> >
> > cc'ing Peter with whom I've discussed this just recently.
>
> Interesting appoach, need to check if that works. I haven't tried that
> yet. Though, that needs some rework of the kernel code as some high
> priority code depends on the translation and that would cause kind of
> priority inversion. E.g. an interrupt handler cannot wait until a
> dpa-to-spa conversion is done.
>

This is not about running it in user space, but about running the code
in an unprivileged sandbox. So scheduling wpuldn't really come into
play here.

> For CXL it is only used for region setup in the init path and process
> context. For tracing and error handling those translations are
> disabled. See patch 13/13.
>