From mboxrd@z Thu Jan  1 00:00:00 1970
From: julien.grall@arm.com (Julien Grall)
Date: Mon, 19 Feb 2018 17:21:17 +0000
Subject: [PATCH v4 17/40] KVM: arm64: Move userspace system registers into
 separate function
In-Reply-To: <20180215210332.8648-18-christoffer.dall@linaro.org>
References: <20180215210332.8648-1-christoffer.dall@linaro.org>
 <20180215210332.8648-18-christoffer.dall@linaro.org>
Message-ID: <411af987-97f8-03a4-60ce-6f271e042983@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Christoffer,

On 15/02/18 21:03, Christoffer Dall wrote:
> There's a semantic difference between the EL1 registers that control
> operation of a kernel running in EL1 and EL1 registers that only control
> userspace execution in EL0.  Since we can defer saving/restoring the
> latter, move them into their own function.
> 
> ACTLR_EL1 is not used by a VHE host, so we can move this register into
> the EL1 state which is not saved/restored for a VHE host.

Looking at D10.2.1 (ARM DDI 0487C.a), the statement regarding the use of 
ACTLR_EL1 seems to be less strong than what you state here. It looks 
like it would be possible to have hardware where ACTLR_EL1 would still 
have an effect on host EL0. I also read the comments on the version 2 of 
this patch but I wasn't able to find what I missing.

Cheers,

-- 
Julien Grall