linux-kernel - Re: [PATCH 1/2] pvpanic: introduce crashloaded for pvpanic

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Message-ID: <87h80pi5hf.fsf@dusky.pond.sub.org>
Date:   Tue, 21 Jan 2020 09:22:20 +0100
From:   Markus Armbruster <armbru@...hat.com>
To:     zhenwei pi <pizhenwei@...edance.com>
Cc:     pbonzini@...hat.com, yelu@...edance.com, libvir-list@...hat.com,
        gregkh@...uxfoundation.org, qemu-devel@...gnu.org,
        linux-kernel@...r.kernel.org, mprivozn@...hat.com
Subject: Re: [PATCH 1/2] pvpanic: introduce crashloaded for pvpanic

zhenwei pi <pizhenwei@...edance.com> writes:

> Add bit 1 for pvpanic. This bit means that guest hits a panic, but
> guest wants to handle error by itself. Typical case: Linux guest runs
> kdump in panic. It will help us to separate the abnormal reboot from
> normal operation.
>
> Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> ---
>  docs/specs/pvpanic.txt | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/docs/specs/pvpanic.txt b/docs/specs/pvpanic.txt
> index c7bbacc778..bdea68a430 100644
> --- a/docs/specs/pvpanic.txt
> +++ b/docs/specs/pvpanic.txt
> @@ -16,8 +16,12 @@ pvpanic exposes a single I/O port, by default 0x505. On read, the bits
>  recognized by the device are set. Software should ignore bits it doesn't
>  recognize. On write, the bits not recognized by the device are ignored.
>  Software should set only bits both itself and the device recognize.

Guest software, I presume.

> -Currently, only bit 0 is recognized, setting it indicates a guest panic
> -has happened.
> +
> +Bit Definition
> +--------------
> +bit 0: setting it indicates a guest panic has happened.
> +bit 1: named crashloaded. setting it indicates a guest panic and run
> +       kexec to handle error by guest itself.

Suggest to scratch "named crashloaded."

The whole file is rather terse.  I figure that's okay as along as
there's just "guest panicked", because "kernel panic" is obvious enough.
The addition of "panicked, handling with kexec" makes it less obvious.
The commit message provides a bit more guidance.  Could that be worked
into this file?

>  
>  ACPI Interface
>  --------------