Date:   Thu, 10 Feb 2022 17:57:19 -0800
From:   Atish Patra <atishp@...shpatra.org>
To:     Heiko Stübner <heiko@...ech.de>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>, Wei Fu <wefu@...hat.com>,
        liush <liush@...winnertech.com>, Guo Ren <guoren@...nel.org>,
        Anup Patel <anup@...infault.org>,
        Drew Fustini <drew@...gleboard.org>,
        Christoph Hellwig <hch@....de>, Arnd Bergmann <arnd@...db.de>,
        Chen-Yu Tsai <wens@...e.org>,
        Maxime Ripard <maxime@...no.tech>,
        Greg Favor <gfavor@...tanamicro.com>,
        Andrea Mondelli <andrea.mondelli@...wei.com>,
        Jonathan Behrens <behrensj@....edu>,
        Xinhaoqu <xinhaoqu@...wei.com>,
        Bill Huffman <huffman@...ence.com>,
        Nick Kossifidis <mick@....forth.gr>,
        Allen Baum <allen.baum@...erantotech.com>,
        Josh Scheid <jscheid@...tanamicro.com>,
        Richard Trauben <rtrauben@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Christoph Muellner <cmuellner@...ux.com>,
        Philipp Tomsich <philipp.tomsich@...ll.eu>
Subject: Re: [PATCH v6 08/14] riscv: move boot alternatives to a slightly
 earlier position

On Thu, Feb 10, 2022 at 5:11 PM Heiko Stübner <heiko@...ech.de> wrote:
>
> Hi Atish,
>
> Am Donnerstag, 10. Februar 2022, 23:42:35 CET schrieb Atish Patra:
> > On Wed, Feb 9, 2022 at 4:39 AM Heiko Stuebner <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.
> > >
> > > 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
> >
> > 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 ?
>
> The issue I see is, we we have the soc_early_init [0] running
> directly after this and the one user I see [1] already wants to
> ioremap io-memory at this stage.
>

Kendryte is always a special case. IIRC, ioremap is done so early
so that it can use all 8MB of SRAM.

> So judging by the fact that more early-inits will get added
> in the future I do guess we should've set up the io-memory
> page-type by this point?
>

I hope there won't be :). For any normal mmu capable SoC, I don't
see why that would be required.

>
> Heiko
>
> [0] https://elixir.bootlin.com/linux/latest/source/arch/riscv/kernel/soc.c#L14
> [1] https://elixir.bootlin.com/linux/latest/source/drivers/soc/canaan/k210-sysctl.c#L66
>
> > 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
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> >
> >
> >
> >
>
>
>
>


-- 
Regards,
Atish

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