Subject: Re: [PATCH 3/9] KVM: arm64: Implement PV_FEATURES call

From: Marc Zyngier <[email-masked]>
Date: Sat, 3 Aug 2019 12:21:24 +0100

On Fri,  2 Aug 2019 15:50:11 +0100
Steven Price <[email-masked]> wrote:

> This provides a mechanism for querying which paravirtualized features
> are available in this hypervisor.
> 
> Also add the header file which defines the ABI for the paravirtualized
> clock features we're about to add.
> 
> Signed-off-by: Steven Price <[email-masked]>
> ---
>  arch/arm64/include/asm/pvclock-abi.h | 20 ++++++++++++++++++++
>  include/linux/arm-smccc.h            | 14 ++++++++++++++
>  virt/kvm/arm/hypercalls.c            |  9 +++++++++
>  3 files changed, 43 insertions(+)
>  create mode 100644 arch/arm64/include/asm/pvclock-abi.h
> 
> diff --git a/arch/arm64/include/asm/pvclock-abi.h b/arch/arm64/include/asm/pvclock-abi.h
> new file mode 100644
> index 000000000000..1f7cdc102691
> --- /dev/null
> +++ b/arch/arm64/include/asm/pvclock-abi.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (C) 2019 Arm Ltd. */
> +
> +#ifndef __ASM_PVCLOCK_ABI_H
> +#define __ASM_PVCLOCK_ABI_H
> +
> +/* The below structures and constants are defined in ARM DEN0057A */
> +
> +struct pvclock_vcpu_stolen_time_info {
> +	__le32 revision;
> +	__le32 attributes;
> +	__le64 stolen_time;
> +	/* Structure must be 64 byte aligned, pad to that size */
> +	u8 padding[48];
> +} __packed;
> +
> +#define PV_VM_TIME_NOT_SUPPORTED	-1

Isn't the intent for this to be the same value as
SMCCC_RET_NOT_SUPPORTED?

> +#define PV_VM_TIME_INVALID_PARAMETERS	-2

It overlaps with SMCCC_RET_NOT_REQUIRED. Is that a problem? Should we
consider a spec change for this?

> +
> +#endif
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 080012a6f025..e7f129f26ebd 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -45,6 +45,7 @@
>  #define ARM_SMCCC_OWNER_SIP		2
>  #define ARM_SMCCC_OWNER_OEM		3
>  #define ARM_SMCCC_OWNER_STANDARD	4
> +#define ARM_SMCCC_OWNER_STANDARD_HYP	5
>  #define ARM_SMCCC_OWNER_TRUSTED_APP	48
>  #define ARM_SMCCC_OWNER_TRUSTED_APP_END	49
>  #define ARM_SMCCC_OWNER_TRUSTED_OS	50
> @@ -302,5 +303,18 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
>  #define SMCCC_RET_NOT_SUPPORTED			-1
>  #define SMCCC_RET_NOT_REQUIRED			-2
>  
> +/* Paravirtualised time calls (defined by ARM DEN0057A) */
> +#define ARM_SMCCC_HV_PV_FEATURES				\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
> +			   ARM_SMCCC_SMC_64,			\
> +			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
> +			   0x20)
> +
> +#define ARM_SMCCC_HV_PV_TIME_ST					\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
> +			   ARM_SMCCC_SMC_64,			\
> +			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
> +			   0x22)
> +
>  #endif /*__ASSEMBLY__*/
>  #endif /*__LINUX_ARM_SMCCC_H*/
> diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
> index f875241bd030..2906b2df99df 100644
> --- a/virt/kvm/arm/hypercalls.c
> +++ b/virt/kvm/arm/hypercalls.c
> @@ -5,6 +5,7 @@
>  #include <linux/kvm_host.h>
>  
>  #include <asm/kvm_emulate.h>
> +#include <asm/pvclock-abi.h>
>  
>  #include <kvm/arm_hypercalls.h>
>  #include <kvm/arm_psci.h>
> @@ -48,6 +49,14 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>  				break;
>  			}
>  			break;
> +		case ARM_SMCCC_HV_PV_FEATURES:
> +			val = SMCCC_RET_SUCCESS;
> +			break;
> +		}
> +		break;
> +	case ARM_SMCCC_HV_PV_FEATURES:
> +		feature = smccc_get_arg1(vcpu);
> +		switch (feature) {
>  		}
>  		break;
>  	default:

Thanks,

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

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