linux-kernel - Re: [PATCH v3] RISC-V: enable XIP

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Date:   Tue, 22 Dec 2020 07:09:01 +0100
From:   Vitaly Wool <vitaly.wool@...sulko.com>
To:     Bin Meng <bmeng.cn@...il.com>
Cc:     linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Bin Meng <bin.meng@...driver.com>,
        Anup Patel <anup@...infault.org>,
        Alistair Francis <alistair.francis@....com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Nicolas Pitre <nico@...xnic.net>
Subject: Re: [PATCH v3] RISC-V: enable XIP

On Tue, Dec 22, 2020 at 2:44 AM Bin Meng <bmeng.cn@...il.com> wrote:
>
> Hi Vitaly,
>
> On Tue, Dec 22, 2020 at 4:39 AM Vitaly Wool <vitaly.wool@...sulko.com> wrote:
> >
> > Introduce XIP (eXecute In Place) support for RISC-V platforms.
> > It allows code to be executed directly from non-volatile storage
> > directly addressable by the CPU, such as QSPI NOR flash which can
> > be found on many RISC-V platforms. This makes way for significant
> > optimization of RAM footprint. The XIP kernel is not compressed
> > since it has to run directly from flash, so it will occupy more
> > space on the non-volatile storage to The physical flash address
> > used to link the kernel object files and for storing it has to
> > be known at compile time and is represented by a Kconfig option.
> >
> > XIP on RISC-V will currently only work on MMU-enabled kernels.
> >
> > Changed in v2:
> > - dedicated macro for XIP address fixup when MMU is not enabled yet
> >   o both for 32-bit and 64-bit RISC-V
> > - SP is explicitly set to a safe place in RAM before __copy_data call
> > - removed redundant alignment requirements in vmlinux-xip.lds.S
> > - changed long -> uintptr_t typecast in __XIP_FIXUP macro.
> >
> > Changed in v3:
> > - rebased against latest for-next
> > - XIP address fixup macro now takes an argument
> > - SMP related fixes
>
> The above changelogs should go below ---

That is very fair, thanks. Will do that for v4.

~Vitaly

> > Signed-off-by: Vitaly Wool <vitaly.wool@...sulko.com>
> > ---
> >  arch/riscv/Kconfig                  |  46 ++++++++-
> >  arch/riscv/Makefile                 |   8 +-
> >  arch/riscv/boot/Makefile            |  13 +++
> >  arch/riscv/include/asm/pgtable.h    |  56 +++++++++--
> >  arch/riscv/kernel/cpu_ops_sbi.c     |   3 +
> >  arch/riscv/kernel/head.S            |  69 +++++++++++++-
> >  arch/riscv/kernel/head.h            |   3 +
> >  arch/riscv/kernel/setup.c           |   8 +-
> >  arch/riscv/kernel/vmlinux-xip.lds.S | 132 ++++++++++++++++++++++++++
> >  arch/riscv/kernel/vmlinux.lds.S     |   6 ++
> >  arch/riscv/mm/init.c                | 142 +++++++++++++++++++++++++---
> >  11 files changed, 460 insertions(+), 26 deletions(-)
> >  create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
> >
>
> Regards,
> Bin