linux-kernel - Re: [PATCH v1 00/24] Opt-in always-on nVHE hypervisor

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Date:   Wed, 11 Nov 2020 14:32:50 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Dennis Zhou <dennis@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Quentin Perret <qperret@...gle.com>,
        Andrew Scull <ascull@...gle.com>,
        Andrew Walbran <qwandor@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v1 00/24] Opt-in always-on nVHE hypervisor

Hi David,

On 2020-11-09 11:32, David Brazdil wrote:
> As we progress towards being able to keep guest state private to the
> host running nVHE hypervisor, this series allows the hypervisor to
> install itself on newly booted CPUs before the host is allowed to run
> on them.
> 
> All functionality described below is opt-in, guarded by an early param
> 'kvm-arm.protected'. Future patches specific to the new "protected" 
> mode
> should be hidden behind the same param.
> 
> The hypervisor starts trapping host SMCs and intercepting host's PSCI
> CPU_ON/OFF/SUSPEND calls. It replaces the host's entry point with its
> own, initializes the EL2 state of the new CPU and installs the nVHE hyp
> vector before ERETing to the host's entry point.
> 
> The kernel checks new cores' features against the finalized system
> capabilities. To avoid the need to move this code/data to EL2, the
> implementation only allows to boot cores that were online at the time 
> of
> KVM initialization and therefore had been checked already.
> 
> Other PSCI SMCs are forwarded to EL3, though only the known set of SMCs
> implemented in the kernel is allowed. Non-PSCI SMCs are also forwarded
> to EL3. Future changes will need to ensure the safety of all SMCs wrt.
> private guests.
> 
> The host is still allowed to reset EL2 back to the stub vector, eg. for
> hibernation or kexec, but will not disable nVHE when there are no VMs.
> 
> Tested on Rock Pi 4b, based on 5.10-rc3.

I think I've gone through most of the patches. When you respin this
series, you may want to do so on top of my host EL2 entry rework [1],
which change a few things you currently rely on.

If anything in there doesn't work for you, please let me know.

Thanks,

         M.

[1] https://lore.kernel.org/kvm/20201109175923.445945-1-maz@kernel.org/
-- 
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