Re: [PATCH RFC/RFT 0/3] efi/libstub: arm32: Remove dependency on dram_base

From: Grant Likely <grant.likely@arm.com>
To: Ard Biesheuvel <ardb@kernel.org>, linux-efi@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org,
	Maxim Uvarov <maxim.uvarov@linaro.org>,
	Heinrich Schuchardt <xypron.glpk@gmx.de>,
	Atish Patra <atish.patra@wdc.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Francois Ozog <francois.ozog@linaro.org>,
	Etienne CARRIERE <etienne.carriere@st.com>,
	Takahiro Akashi <takahiro.akashi@linaro.org>,
	Patrice CHOTARD <patrice.chotard@st.com>,
	Sumit Garg <sumit.garg@linaro.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	Christophe Priouzeau <christophe.priouzeau@linaro.org>,
	Rouven Czerwinski <r.czerwinski@pengutronix.de>,
	Patrick DELAUNAY <patrick.delaunay@st.com>, nd <nd@arm.com>
Subject: Re: [PATCH RFC/RFT 0/3] efi/libstub: arm32: Remove dependency on dram_base
Date: Wed, 9 Sep 2020 16:25:36 +0100	[thread overview]
Message-ID: <5b4c9d0f-d0c1-4627-d000-3bdf093b252a@arm.com> (raw)
In-Reply-To: <20200909151623.16153-1-ardb@kernel.org>

On 09/09/2020 16:16, Ard Biesheuvel wrote:
> Maxim reports boot failures on platforms that describe reserved memory
> regions in DT that are disjoint from system DRAM, and which are converted
> to EfiReservedMemory regions by the EFI subsystem in u-boot.
> 
> As it turns out, the whole notion of discovering the base of DRAM is
> problematic, and it would be better to simply rely on the EFI memory
> allocation routines instead, and derive the FDT and initrd allocation
> limits from the actual placement of the kernel (which is what defines
> the start of the linear region anyway)
> 
> Finally, we should be able to get rid of get_dram_base() entirely.
> However, as RISC-V only just started using it, we will need to address
> that at a later time.

Looks reasonable to me. Presumably all special cases (platform specific 
spin tables, etc) are covered as reserved in the UEFI memory map, correct?

g.

> 
> Cc: Maxim Uvarov <maxim.uvarov@linaro.org>
> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
> Cc: Atish Patra <atish.patra@wdc.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Jens Wiklander <jens.wiklander@linaro.org>
> Cc: Francois Ozog <francois.ozog@linaro.org>
> Cc: Etienne CARRIERE <etienne.carriere@st.com>
> Cc: Takahiro Akashi <takahiro.akashi@linaro.org>
> Cc: Patrice CHOTARD <patrice.chotard@st.com>
> Cc: Sumit Garg <sumit.garg@linaro.org>
> Cc: Grant Likely <Grant.Likely@arm.com>
> Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> Cc: Christophe Priouzeau <christophe.priouzeau@linaro.org>
> Cc: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> Cc: Patrick DELAUNAY <patrick.delaunay@st.com>
> 
> Ard Biesheuvel (3):
>    efi/libstub: Export efi_low_alloc_above() to other units
>    efi/libstub: Use low allocation for the uncompressed kernel
>    efi/libstub: base FDT and initrd placement on image address not DRAM
>      base
> 
>   arch/arm/include/asm/efi.h                |   6 +-
>   arch/arm64/include/asm/efi.h              |   2 +-
>   drivers/firmware/efi/libstub/arm32-stub.c | 177 ++++----------------
>   drivers/firmware/efi/libstub/efi-stub.c   |   2 +-
>   drivers/firmware/efi/libstub/efistub.h    |   3 +
>   drivers/firmware/efi/libstub/relocate.c   |   4 +-
>   6 files changed, 47 insertions(+), 147 deletions(-)
> 