linux-kernel - Re: [RFC PATCH 0/1] Arm Live Firmware activation support

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Message-ID: <20250916-energetic-debonair-mongrel-dfcafb@sudeepholla>
Date: Tue, 16 Sep 2025 15:38:31 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Andre Przywara <andre.przywara@....com>
Cc: Mark Rutland <mark.rutland@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-coco@...ts.linux.dev>,
	Chao Gao <chao.gao@...el.com>, Ard Biesheuvel <ardb@...nel.org>,
	Salman Nabi <salman.nabi@....com>
Subject: Re: [RFC PATCH 0/1] Arm Live Firmware activation support

On Wed, Jun 25, 2025 at 03:27:21PM +0100, Andre Przywara wrote:
> Hi,
> 
> (please feel free to add people interested on this from the x86 side
> as you see fit)
> 
> this is a proposal for a driver for the Arm Live Firmware Activation (LFA)
> specification[1]. LFA provides an interface to allow "activating" firmware
> updates without a reboot.
> In contrast to Intel's TDX [2] approach (which seems only concerned about
> some confidential computing related firmware blob), and even OCP's
> "impactless" updates[3], the Arm approach just lists a number of
> "activatable" firmware images, and does not limit their scope. In
> particular those updates can (and will) be for firmware bits used by the
> application processors (which OCP seems to rule out), including runtime
> secure firmware (TF-A/BL31), confidential compute firmware, and
> potentially even UEFI runtime firmware.
> Initially we have the whole chain demoing the Arm Confidential Computing
> firmware (RMM) update, which is conceptually the same as Intel's TDX
> proposal.
> 
> So our design approach is to create a directory under /sys/firmware, and
> just list all images there, as directories named by their GUID.
> Then the properties of each image can be queried and the activation
> triggered by the sysfs files inside each directory. For details see the
> commit message of the patch.
> This is admittedly a somewhat raw interface, though even in that form
> it's good enough for testing. Eventually I would expect some fwupd
> plugin to wrap this nicely for any admins or end users.
> 
> The purpose of this RFC is to get some feedback on the feasibility of
> this interface, and to understand how this would relate to the other two
> approaches (TDX + OCP "impactless" updates).
> 

Thanks for the details and I agree we need opinions from x86 community
if possible but definitely from cloud/hyperscale community using these
user interfaces ? While x86 and Arm may provide its own user interface,
are hyperscale community happy with that ? I briefly read the unified
(arch agnostic) requirements specification [3] but will there be a
requirement to have a unified user interface from the OS ?

We don't want to define something Arm specific to just abandon it quickly
if and when hyperscale community comes back with such a request for unified
user interface.

I am not against having Arm specific interface, just getting clarification
in terms of requirements even before diving into technical review of the
patch here.

Anyone from hyperscale community ? Please provide directions here.

-- 
Regards,
Sudeep