Re: [PATCH v2] xen: arm: doc: Add firmware requirements

From: Julien Grall <julien.grall@arm.com>
To: Dirk Behme <dirk.behme@de.bosch.com>, xen-devel@lists.xen.org
Cc: sstabellini@kernel.org
Subject: Re: [PATCH v2] xen: arm: doc: Add firmware requirements
Date: Fri, 22 Apr 2016 17:57:09 +0100	[thread overview]
Message-ID: <571A57E5.4000809@arm.com> (raw)
In-Reply-To: <1461305729-12459-1-git-send-email-dirk.behme@de.bosch.com>

Hi Dirk,

On 22/04/16 07:15, Dirk Behme wrote:
> Add a section about what the firmware should do in EL3 before starting Xen.
>
> E.g. on ARM Linux the HVC instruction is used to trap into Xen. As this

I would rather say "E.g guest will use HVC instruction to issue hypercall".

> can be set only at EL3, i.e. outside from Xen, document this boot requirement.

s/outside from/outside/

>
> Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
> ---
>   docs/misc/arm/booting.txt | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
>
> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
> index 9802e5e..b0ff305 100644
> --- a/docs/misc/arm/booting.txt
> +++ b/docs/misc/arm/booting.txt
> @@ -23,6 +23,21 @@ The exceptions to this on 32-bit ARM are as follows:
>
>   There are no exception on 64-bit ARM.
>
> +
> +Firmware/bootloader requirements
> +--------------------------------
> +
> +Xen relies on some settings the firmware has to do in EL3 before starting

I would replace "do" by "configure".

> +Xen.
> +
> +* EL2: Xen must be entered in NS EL2 mode

I would drop "EL2: " as it's not clear what it stands for. Same for 
"HCE:" below.

> +
> +* HCE: It has to be ensured that the Secure Configuration Register
> +       has the HVC instructions enabled at EL1 and above
> +       ARM32: SCR.HCE == 1
> +       ARM64: SCR_EL3.HCE == 1

I would simplify the description: "The bit SCR_EL3.HCR (resp. SCR.HCE 
for 32-bit ARM) must be set to 1."

> +
> +
>   [1] linux/Documentation/arm/Booting
>   Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
>
>

Regards,

-- 
Julien Grall

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