Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230406220206.3067006-1-chenjiahao16@huawei.com> <20230406220206.3067006-3-chenjiahao16@huawei.com>
In-Reply-To: <20230406220206.3067006-3-chenjiahao16@huawei.com>
From:   Guo Ren <guoren@kernel.org>
Date:   Fri, 7 Apr 2023 16:34:31 +0800
Message-ID: <CAJF2gTR-3a6X2_XPWzOaDdfMehQnQhU0aAxOXOPqOJ=CM5fFUw@mail.gmail.com>
Subject: Re: [PATCH -next v3 2/2] docs: kdump: Update the crashkernel
 description for riscv
To:     Chen Jiahao <chenjiahao16@huawei.com>
Cc:     linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
        kexec@lists.infradead.org, linux-doc@vger.kernel.org,
        paul.walmsley@sifive.com, palmer@dabbelt.com,
        conor.dooley@microchip.com, heiko@sntech.de, bjorn@rivosinc.com,
        alex@ghiti.fr, akpm@linux-foundation.org, atishp@rivosinc.com,
        bhe@redhat.com, thunder.leizhen@huawei.com, horms@kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Reviewed-by: Guo Ren <guoren@kernel.org>

On Thu, Apr 6, 2023 at 10:05=E2=80=AFPM Chen Jiahao <chenjiahao16@huawei.co=
m> wrote:
>
> Now "crashkernel=3D" parameter on riscv has been updated to support
> crashkernel=3DX,[high,low]. Through which we can reserve memory region
> above/within 32bit addressible DMA zone.
>
> Here update the parameter description accordingly.
>
> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentat=
ion/admin-guide/kernel-parameters.txt
> index 54702bd488eb..41865aae9eaa 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -866,7 +866,7 @@
>                         memory region [offset, offset + size] for that ke=
rnel
>                         image. If '@offset' is omitted, then a suitable o=
ffset
>                         is selected automatically.
> -                       [KNL, X86-64, ARM64] Select a region under 4G fir=
st, and
> +                       [KNL, X86-64, ARM64, RISCV] Select a region under=
 4G first, and
>                         fall back to reserve region above 4G when '@offse=
t'
>                         hasn't been specified.
>                         See Documentation/admin-guide/kdump/kdump.rst for=
 further details.
> @@ -879,14 +879,14 @@
>                         Documentation/admin-guide/kdump/kdump.rst for an =
example.
>
>         crashkernel=3Dsize[KMG],high
> -                       [KNL, X86-64, ARM64] range could be above 4G. All=
ow kernel
> -                       to allocate physical memory region from top, so c=
ould
> -                       be above 4G if system have more than 4G ram insta=
lled.
> -                       Otherwise memory region will be allocated below 4=
G, if
> -                       available.
> +                       [KNL, X86-64, ARM64, RISCV] range could be above =
4G.
> +                       Allow kernel to allocate physical memory region f=
rom top,
> +                       so could be above 4G if system have more than 4G =
ram
> +                       installed. Otherwise memory region will be alloca=
ted
> +                       below 4G, if available.
>                         It will be ignored if crashkernel=3DX is specifie=
d.
>         crashkernel=3Dsize[KMG],low
> -                       [KNL, X86-64, ARM64] range under 4G. When crashke=
rnel=3DX,high
> +                       [KNL, X86-64, ARM64, RISCV] range under 4G. When =
crashkernel=3DX,high
>                         is passed, kernel could allocate physical memory =
region
>                         above 4G, that cause second kernel crash on syste=
m
>                         that require some amount of low memory, e.g. swio=
tlb
> @@ -897,6 +897,7 @@
>                         size is platform dependent.
>                           --> x86: max(swiotlb_size_or_default() + 8MiB, =
256MiB)
>                           --> arm64: 128MiB
> +                         --> riscv: 128MiB
>                         This one lets the user specify own low range unde=
r 4G
>                         for second kernel instead.
>                         0: to disable low allocation.
> --
> 2.31.1
>


--=20
Best Regards
 Guo Ren