linux-kernel - Re: [PATCHv2 1/4] arm64: smccc: Add SMCCC pv-vcpu-state function call IDs

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Date:   Mon, 12 Jul 2021 15:22:40 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Will Deacon <will@...nel.org>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCHv2 1/4] arm64: smccc: Add SMCCC pv-vcpu-state function call IDs

On Fri, 09 Jul 2021 05:37:10 +0100,
Sergey Senozhatsky <senozhatsky@...omium.org> wrote:
> 
> Add the definitions of the SMCCC functions that will be
> used to paravirt VCPU state configuration.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
>  include/linux/arm-smccc.h | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 7d1cabe15262..dbf0d658e54a 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -177,6 +177,24 @@
>  			   ARM_SMCCC_OWNER_STANDARD,		\
>  			   0x53)
>  
> +#define ARM_SMCCC_HV_PV_VCPU_STATE_FEATURES			\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
> +			   ARM_SMCCC_SMC_64,			\
> +			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
> +			   0x60)
> +
> +#define ARM_SMCCC_HV_PV_VCPU_STATE_INIT			\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
> +			   ARM_SMCCC_SMC_64,			\
> +			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
> +			   0x61)
> +
> +#define ARM_SMCCC_HV_PV_VCPU_STATE_RELEASE			\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
> +			   ARM_SMCCC_SMC_64,			\
> +			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
> +			   0x62)
> +

This is definitely the *wrong* namespace for this. The "STANDARD_HYP"
space is owned by ARM for hypercalls that are implementable by any
hypervisors, and for which there is an ARM-owned specification.

Unless you plan to get this adopted as an ARM spec (pretty doubtful),
this should go instead in the KVM-specific space, which currently has
a single user (the PTP stuff), although I plan to add a couple more
shortly.

	M.

-- 
Without deviation from the norm, progress is not possible.