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

[Atish Patra <atishp@atishpatra.org>]

On Wed, Feb 9, 2022 at 4:39 AM Heiko Stuebner <heiko@sntech.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.
>
> Signed-off-by: Heiko Stuebner <heiko@sntech.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

Do you really need this early ?
if non-smp configuration is the only option, Can you do it in
setup_arch() after riscv_fill_hwcap() is called ?

By doing that, we can unify the cpu feature probing and you don't need
a separate DT parsing just for svpbmt.

>         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)
> --
> 2.30.2
>
>
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-- 
Regards,
Atish