linux-kernel - Re: [PATCH v4 17/21] KVM: arm64: Document HVC_VHE

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Message-ID: <20210118132935.mutemf7j7wtyz7wz@google.com>
Date:   Mon, 18 Jan 2021 13:29:35 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Ajay Patil <pajay@....qualcomm.com>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        Srinivas Ramana <sramana@...eaurora.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v4 17/21] KVM: arm64: Document HVC_VHE_RESTART stub
 hypercall

On Mon, Jan 18, 2021 at 09:45:29AM +0000, Marc Zyngier wrote:
> For completeness, let's document the HVC_VHE_RESTART stub.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
Acked-by: David Brazdil <dbrazdil@...gle.com>

> ---
>  Documentation/virt/kvm/arm/hyp-abi.rst | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/arm/hyp-abi.rst b/Documentation/virt/kvm/arm/hyp-abi.rst
> index 83cadd8186fa..1ba628baf11b 100644
> --- a/Documentation/virt/kvm/arm/hyp-abi.rst
> +++ b/Documentation/virt/kvm/arm/hyp-abi.rst
> @@ -58,6 +58,15 @@ these functions (see arch/arm{,64}/include/asm/virt.h):
>    into place (arm64 only), and jump to the restart address while at HYP/EL2.
>    This hypercall is not expected to return to its caller.
>  
> +* ::
> +
> +    x0 = HVC_VHE_RESTART (arm64 only)
> +
> +  Attempt to upgrade the kernel's exception level from EL1 to EL2 by enabling
> +  the VHE mode. This is conditioned by the CPU supporting VHE, the EL2 MMU
> +  being off, and VHE not being disabled by any other mean (comment line option,
'means' (both singular and plural), and 'command line'

> +  for example).
> +
>  Any other value of r0/x0 triggers a hypervisor-specific handling,
>  which is not documented here.
>  
> -- 
> 2.29.2
>