Re: [PATCH v3 06/23] kvm: arm64: Add kvm-arm.protected early kernel parameter

[Sudeep Holla <sudeep.holla@arm.com>]

On Thu, Nov 26, 2020 at 03:54:04PM +0000, David Brazdil wrote:
> Add an early parameter that allows users to opt into protected KVM mode
> when using the nVHE hypervisor. In this mode, guest state will be kept
> private from the host. This will primarily involve enabling stage-2
> address translation for the host, restricting DMA to host memory, and
> filtering host SMCs.
> 
> Capability ARM64_PROTECTED_KVM is set if the param is passed, CONFIG_KVM
> is enabled and the kernel was not booted with VHE.
> 
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
>  .../admin-guide/kernel-parameters.txt         |  5 ++++
>  arch/arm64/include/asm/cpucaps.h              |  3 +-
>  arch/arm64/include/asm/virt.h                 |  8 +++++
>  arch/arm64/kernel/cpufeature.c                | 29 +++++++++++++++++++
>  arch/arm64/kvm/arm.c                          |  4 ++-
>  5 files changed, 47 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 526d65d8573a..06c89975c29c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2259,6 +2259,11 @@
>  			for all guests.
>  			Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
>  
> +	kvm-arm.protected=
> +			[KVM,ARM] Allow spawning protected guests whose state
> +			is kept private from the host. Only valid for non-VHE.
> +			Default is 0 (disabled).
> +

Sorry for being pedantic. Can we reword this to say valid for
!CONFIG_ARM64_VHE ? I read this as valid only for non-VHE hardware, it may
be just me, but if you agree please update so that it doesn't give remote
idea that it is not valid on VHE enabled hardware.

I was trying to run this on the hardware and was trying to understand the
details on how to do that.

-- 
Regards,
Sudeep