Re: [PATCH 1/9] ARM: enable secure platform-only erratas

From: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Russell King - ARM Linux <linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org>
Cc: "Michał Mirosław"
	<mirq-linux-CoA6ZxLDdyEEUmgCuDUIdw@public.gmane.org>,
	linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: Re: [PATCH 1/9] ARM: enable secure platform-only erratas
Date: Wed, 20 Dec 2017 15:49:39 +0300	[thread overview]
Message-ID: <21964ae9-4c60-36b2-627d-04e4e975a38d@gmail.com> (raw)
In-Reply-To: <20171219232810.GI10595-l+eeeJia6m9URfEZ8mYm6t73F7V6hmMc@public.gmane.org>

On 20.12.2017 02:28, Russell King - ARM Linux wrote:
> On Thu, Oct 05, 2017 at 09:16:12PM +0300, Dmitry Osipenko wrote:
>> On 20.07.2017 03:29, Michał Mirosław wrote:
>>> Allow secure-only erratas to be used in multiarch kernel.
>>>
>>> Signed-off-by: Michał Mirosław <mirq-linux-CoA6ZxLDdyEEUmgCuDUIdw@public.gmane.org>
>>> ---
>>>  arch/arm/Kconfig | 20 ++++++++++++++------
>>>  1 file changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>>> index a208bfe367b5..a1eff866550b 100644
>>> --- a/arch/arm/Kconfig
>>> +++ b/arch/arm/Kconfig
>>> @@ -696,6 +696,14 @@ config ARCH_MULTI_CPU_AUTO
>>>  
>>>  endmenu
>>>  
>>> +config ARCH_ASSUME_SECURE_PLATFORM
>>> +	bool "Enable ERRATAs using secure-only registers"
>>> +	default !ARCH_MULTIPLATFORM
>>
>> I think default should always be "Yes" and this option shouldn't affect
>> multiplatform kernels. So a multiplatform kernel wouldn't be an option
>> for your device.
> 
> No, that changes the current behaviour.
> 
> Current behaviour is for the secure-only errata to be disabled when the
> multi-platform option is enabled, because multi-platform kernels have to
> be able to run in the non-secure world.  Defaulting this option to "yes"
> means that these errata become visible.

Indeed, I got it inverted.

> I have to wonder why you need this though - your patches seem to be
> targetting a platform that runs in non-secure world, and enabling these
> errata would make the kernel non-bootable on your platform.

Perhaps because Michał made the Tegra's CPU reset handler hardcoded to either
secure or to non-secure case based on the kernels configuration. I've showed how
we can get rid of that inflexibility in [0], maybe Michał could pick up the idea
in the next iteration of the patches.

[0] https://marc.info/?l=linux-tegra&m=151371042522835