Re: [PATCH v2 07/15] efi/libstub: Add generic arch callbacks for DRTM

From: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: "Alexandre Ghiti" <alex@ghiti.fr>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"David Sterba" <dsterba@suse.com>,
	"Ilias Apalodimas" <ilias.apalodimas@linaro.org>,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-doc@vger.kernel.org, linux-efi@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Paul Walmsley" <pjw@kernel.org>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	"Simon Glass" <sjg@chromium.org>,
	"Shuah Khan" <skhan@linuxfoundation.org>,
	"Nick Terrell" <terrelln@fb.com>, "Will Deacon" <will@kernel.org>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Conor Dooley" <conor.dooley@microchip.com>,
	linux-integrity@vger.kernel.org,
	"Palmer Dabbelt" <palmer@rivosinc.com>,
	patches@lists.linux.dev, "Piotr Król" <piotr.krol@3mdeb.com>,
	"Ross Philipson" <ross.philipson@gmail.com>,
	"Sami Tolvanen" <samitolvanen@google.com>,
	"Song Shuai" <songshuaishuai@tinylab.org>
Subject: Re: [PATCH v2 07/15] efi/libstub: Add generic arch callbacks for DRTM
Date: Wed, 21 Oct 2026 09:51:55 -0700	[thread overview]
Message-ID: <20261021095155.00003fc2@oss.qualcomm.com> (raw)
In-Reply-To: <7-v2-989a18390eb1+486-arm64_drtm_jgg@nvidia.com>

On Fri,  2 Oct 2026 20:31:44 -0300
Jason Gunthorpe <jgg@nvidia.com> wrote:

> If the architecture supports an EFI stub launched version of DRTM, it
> can select the kconfig and provide the hooks under its architecture
> build.
> 
> Have the common code parse a drtm=enforce|auto|off kernel command line
> parameter to set the boot behavior. Support commas in the args list since
> there will be more options here down the road.
> 
> efi_drtm_prepare() is called before doing any decompression or image
> relocation. It should figure out if DRTM is supported, policy-permitted,
> and how much memory efi_drtm_get_extra_size() should return.
> 
> The image handling is revised to allocate extra_size at the end of
> the normal image. The architecture can use this to store any
> information needed for the DRTM flow. It is always contiguous with
> Image, which is a requirement of ARM's specification.
> 
> efi_drtm_prepare_launch() is called while still in EFI boot services after
> Image is fully prepared in its final location.
> 
> efi_drtm_launch() is called after exiting boot services and must
> jump into the kernel through the DRTM flow. If it returns, then the
> normal launch is tried (auto mode).
> 
> The extra_size is allocated directly after the Image. Handle the
> trivial zboot flow now, and vmlinux in the following patch.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Seems fine to me.  Some of the functions affected have annoyingly
complex flows already but this isn't obviously making things worse!

Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>