linux-kernel - Re: [PATCH v4 00/23] arm64: Virtualization Host Extension support

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Date:	Thu, 11 Feb 2016 20:07:01 +0100
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Mark Rutland <mark.rutland@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
	Alex Bennée <alex.bennee@...aro.org>
Subject: Re: [PATCH v4 00/23] arm64: Virtualization Host Extension support

On Thu, Feb 11, 2016 at 06:39:41PM +0000, Marc Zyngier wrote:
> ARMv8.1 comes with the "Virtualization Host Extension" (VHE for
> short), which enables simpler support of Type-2 hypervisors.
> 
> This extension allows the kernel to directly run at EL2, and
> significantly reduces the number of system registers shared between
> host and guest, reducing the overhead of virtualization.
> 
> In order to have the same kernel binary running on all versions of the
> architecture, this series makes heavy use of runtime code patching.
> 
> The first 22 patches massage the KVM code to deal with VHE and enable
> Linux to run at EL2. The last patch catches an ugly case when VHE
> capable CPUs are paired with some of their less capable siblings. This
> should never happen, but hey...
> 
> I have deliberately left out some of the more "advanced"
> optimizations, as they are likely to distract the reviewer from the
> core infrastructure, which is what I care about at the moment.
> 
> Note: GDB is currently busted on VHE systems, as it checks for version
>       6 on the debug architecture, while VHE is version 7. The
>       binutils people are on the case.
> 
> This has been tested on the FVP_Base_SLV-V8-A model, and based on
> v4.5-rc3 + kvmarm/master. I've put a branch out on:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git kvm-arm64/vhe

I'm happy with this series as it stands, we just need someone to take a
look at that debug patch and be happy with it.

Thanks,
-Christoffer