linux-kernel - Re: [PATCH v6 08/14] riscv: move boot alternatives to a slightly earlier position

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Date:   Mon, 07 Mar 2022 16:47:23 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     heiko@...ech.de
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org, wefu@...hat.com,
        liush@...winnertech.com, guoren@...nel.org, atishp@...shpatra.org,
        anup@...infault.org, drew@...gleboard.org,
        Christoph Hellwig <hch@....de>, Arnd Bergmann <arnd@...db.de>,
        wens@...e.org, maxime@...no.tech, gfavor@...tanamicro.com,
        andrea.mondelli@...wei.com, behrensj@....edu, xinhaoqu@...wei.com,
        huffman@...ence.com, mick@....forth.gr,
        allen.baum@...erantotech.com, jscheid@...tanamicro.com,
        rtrauben@...il.com, samuel@...lland.org, cmuellner@...ux.com,
        philipp.tomsich@...ll.eu, heiko@...ech.de
Subject:     Re: [PATCH v6 08/14] riscv: move boot alternatives to a slightly earlier position

On Wed, 09 Feb 2022 04:37:54 PST (-0800), heiko@...ech.de wrote:
> Move the application of boot alternatives to soc_early_init().
> This allows to catch more generic cases of code needing patches
> than doing it in smp_prepare_boot_cpu() and also makes it actually
> work if CONFIG_SMP is disabled for whatever reason.
>
> The position is chosen mainly as it is before the actual soc early
> init runs but also already allows accessing the devicetree
> via fdt_* functions.

I think this is OK, but it warrants testing on the K210 -- specifically 
the system is in an odd state before soc_early_init (IIRC some of memory 
doesn't work right) so I'm always a bit worried about calling stuff 
there.  I don't have a K210 (or at least a working one), so I'm not 
going to be able to test it.

> Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> ---
>  arch/riscv/kernel/head.S    | 2 ++
>  arch/riscv/kernel/smpboot.c | 2 --
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 2363b43312fc..0e1bb97f9749 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -10,6 +10,7 @@
>  #include <asm/thread_info.h>
>  #include <asm/page.h>
>  #include <asm/pgtable.h>
> +#include <asm/alternative.h>
>  #include <asm/csr.h>
>  #include <asm/cpu_ops_sbi.h>
>  #include <asm/hwcap.h>
> @@ -341,6 +342,7 @@ clear_bss_done:
>  	call kasan_early_init
>  #endif
>  	/* Start the kernel */
> +	call apply_boot_alternatives
>  	call soc_early_init
>  	tail start_kernel
>
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index a6d13dca1403..f1e4948a4b52 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -32,7 +32,6 @@
>  #include <asm/sections.h>
>  #include <asm/sbi.h>
>  #include <asm/smp.h>
> -#include <asm/alternative.h>
>
>  #include "head.h"
>
> @@ -41,7 +40,6 @@ static DECLARE_COMPLETION(cpu_running);
>  void __init smp_prepare_boot_cpu(void)
>  {
>  	init_cpu_topology();
> -	apply_boot_alternatives();
>  }
>
>  void __init smp_prepare_cpus(unsigned int max_cpus)