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From:   Atish Kumar Patra <atishp@rivosinc.com>
Date:   Tue, 21 Nov 2023 00:21:11 -0800
Message-ID: <CAHBxVyG-DK9cDqPedJcR2W2=LQFumQQ_0Z0UUdbbzgju7BaAtg@mail.gmail.com>
Subject: Re: [PATCH v4 4/5] tty: Add SBI debug console support to HVC SBI driver
To:     Jiri Slaby <jirislaby@kernel.org>
Cc:     Anup Patel <apatel@ventanamicro.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Conor Dooley <conor@kernel.org>,
        Andrew Jones <ajones@ventanamicro.com>,
        linux-riscv@lists.infradead.org, linux-serial@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
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On Sun, Nov 19, 2023 at 11:16=E2=80=AFPM Jiri Slaby <jirislaby@kernel.org> =
wrote:
>
> On 18. 11. 23, 4:38, Anup Patel wrote:
> > diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_risc=
v_sbi.c
> > index 31f53fa77e4a..697c981221b5 100644
> > --- a/drivers/tty/hvc/hvc_riscv_sbi.c
> > +++ b/drivers/tty/hvc/hvc_riscv_sbi.c
> ...
> > -static int __init hvc_sbi_console_init(void)
> > +static int hvc_sbi_dbcn_tty_get(uint32_t vtermno, char *buf, int count=
)
> >   {
> > -     hvc_instantiate(0, 0, &hvc_sbi_ops);
> > +     phys_addr_t pa;
> > +
> > +     if (is_vmalloc_addr(buf)) {
>
> I wonder, where does this buf come from, so that you have to check for
> vmalloc?
>

When VMAP_STCK is enabled, stack allocation depends on the vmalloc.
That's why we have to if the buf is allocated using vmalloc.

> > +             pa =3D page_to_phys(vmalloc_to_page(buf)) + offset_in_pag=
e(buf);
> > +             if (PAGE_SIZE < (offset_in_page(buf) + count))
>
> Am I the only one who would prefer:
>    if (count + offset_in_page(buf) > PAGE_SIZE)
> ?
>
> > +                     count =3D PAGE_SIZE - offset_in_page(buf);
> > +     } else {
> > +             pa =3D __pa(buf);
> > +     }
> > +
> > +     return sbi_debug_console_read(count, pa);
> > +}
>
>
> thanks,
> --
> js
> suse labs
>