From mboxrd@z Thu Jan  1 00:00:00 1970
From: christoffer.dall@linaro.org (Christoffer Dall)
Date: Thu, 4 Feb 2016 20:25:17 +0100
Subject: [PATCH v3 23/23] arm64: Panic when VHE and non VHE CPUs coexist
In-Reply-To: <1454522416-6874-24-git-send-email-marc.zyngier@arm.com>
References: <1454522416-6874-1-git-send-email-marc.zyngier@arm.com>
 <1454522416-6874-24-git-send-email-marc.zyngier@arm.com>
Message-ID: <20160204192517.GH13974@cbox>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wed, Feb 03, 2016 at 06:00:16PM +0000, Marc Zyngier wrote:
> Having both VHE and non-VHE capable CPUs in the same system
> is likely to be a recipe for disaster.
> 
> If the boot CPU has VHE, but a secondary is not, we won't be
> able to downgrade and run the kernel at EL1. Add CPU hotplug
> to the mix, and this produces a terrifying mess.
> 
> Let's solve the problem once and for all. If you mix VHE and
> non-VHE CPUs in the same system, you deserve to loose, and this
> patch makes sure you don't get a chance.
> 
> This is implemented by storing the kernel execution level in
> a global variable. Secondaries will park themselves in a
> WFI loop if they observe a mismatch. Also, the primary CPU
> will detect that the secondary CPU has died on a mismatched
> execution level. Panic will follow.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>