Re: [PATCH v4 17/18] RISC-V: KVM: add support for FWFT SBI extension

[Andrew Jones <ajones@ventanamicro.com>]

On Mon, Mar 17, 2025 at 06:06:23PM +0100, Clément Léger wrote:
> Add basic infrastructure to support the FWFT extension in KVM.
> 
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>  arch/riscv/include/asm/kvm_host.h          |   4 +
>  arch/riscv/include/asm/kvm_vcpu_sbi.h      |   1 +
>  arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h |  29 +++
>  arch/riscv/include/uapi/asm/kvm.h          |   1 +
>  arch/riscv/kvm/Makefile                    |   1 +
>  arch/riscv/kvm/vcpu_sbi.c                  |   4 +
>  arch/riscv/kvm/vcpu_sbi_fwft.c             | 216 +++++++++++++++++++++
>  7 files changed, 256 insertions(+)
>  create mode 100644 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
>  create mode 100644 arch/riscv/kvm/vcpu_sbi_fwft.c
> 
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index bb93d2995ea2..c0db61ba691a 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -19,6 +19,7 @@
>  #include <asm/kvm_vcpu_fp.h>
>  #include <asm/kvm_vcpu_insn.h>
>  #include <asm/kvm_vcpu_sbi.h>
> +#include <asm/kvm_vcpu_sbi_fwft.h>
>  #include <asm/kvm_vcpu_timer.h>
>  #include <asm/kvm_vcpu_pmu.h>
>  
> @@ -281,6 +282,9 @@ struct kvm_vcpu_arch {
>  	/* Performance monitoring context */
>  	struct kvm_pmu pmu_context;
>  
> +	/* Firmware feature SBI extension context */
> +	struct kvm_sbi_fwft fwft_context;
> +
>  	/* 'static' configurations which are set only once */
>  	struct kvm_vcpu_config cfg;
>  
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> index cb68b3a57c8f..ffd03fed0c06 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> @@ -98,6 +98,7 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_dbcn;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_susp;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta;
> +extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
>  
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
> new file mode 100644
> index 000000000000..9ba841355758
> --- /dev/null
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2025 Rivos Inc.
> + *
> + * Authors:
> + *     Clément Léger <cleger@rivosinc.com>
> + */
> +
> +#ifndef __KVM_VCPU_RISCV_FWFT_H
> +#define __KVM_VCPU_RISCV_FWFT_H
> +
> +#include <asm/sbi.h>
> +
> +struct kvm_sbi_fwft_feature;
> +
> +struct kvm_sbi_fwft_config {
> +	const struct kvm_sbi_fwft_feature *feature;
> +	bool supported;
> +	unsigned long flags;
> +};
> +
> +/* FWFT data structure per vcpu */
> +struct kvm_sbi_fwft {
> +	struct kvm_sbi_fwft_config *configs;
> +};
> +
> +#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
> +
> +#endif /* !__KVM_VCPU_RISCV_FWFT_H */
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index f06bc5efcd79..fa6eee1caf41 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -202,6 +202,7 @@ enum KVM_RISCV_SBI_EXT_ID {
>  	KVM_RISCV_SBI_EXT_DBCN,
>  	KVM_RISCV_SBI_EXT_STA,
>  	KVM_RISCV_SBI_EXT_SUSP,
> +	KVM_RISCV_SBI_EXT_FWFT,
>  	KVM_RISCV_SBI_EXT_MAX,
>  };
>  
> diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
> index 4e0bba91d284..06e2d52a9b88 100644
> --- a/arch/riscv/kvm/Makefile
> +++ b/arch/riscv/kvm/Makefile
> @@ -26,6 +26,7 @@ kvm-y += vcpu_onereg.o
>  kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
>  kvm-y += vcpu_sbi.o
>  kvm-y += vcpu_sbi_base.o
> +kvm-y += vcpu_sbi_fwft.o
>  kvm-y += vcpu_sbi_hsm.o
>  kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
>  kvm-y += vcpu_sbi_replace.o
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index 50be079b5528..0748810c0252 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
>  		.ext_idx = KVM_RISCV_SBI_EXT_STA,
>  		.ext_ptr = &vcpu_sbi_ext_sta,
>  	},
> +	{
> +		.ext_idx = KVM_RISCV_SBI_EXT_FWFT,
> +		.ext_ptr = &vcpu_sbi_ext_fwft,
> +	},
>  	{
>  		.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
>  		.ext_ptr = &vcpu_sbi_ext_experimental,
> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
> new file mode 100644
> index 000000000000..8a7cfe1fe7a7
> --- /dev/null
> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
> @@ -0,0 +1,216 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2025 Rivos Inc.
> + *
> + * Authors:
> + *     Clément Léger <cleger@rivosinc.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/kvm_host.h>
> +#include <asm/cpufeature.h>
> +#include <asm/sbi.h>
> +#include <asm/kvm_vcpu_sbi.h>
> +#include <asm/kvm_vcpu_sbi_fwft.h>
> +
> +struct kvm_sbi_fwft_feature {
> +	/**
> +	 * @id: Feature ID
> +	 */
> +	enum sbi_fwft_feature_t id;
> +
> +	/**
> +	 * @supported: Check if the feature is supported on the vcpu
> +	 *
> +	 * This callback is optional, if not provided the feature is assumed to
> +	 * be supported
> +	 */
> +	bool (*supported)(struct kvm_vcpu *vcpu);
> +
> +	/**
> +	 * @set: Set the feature value
> +	 *
> +	 * Return SBI_SUCCESS on success or an SBI error (SBI_ERR_*)
> +	 *
> +	 * This callback is mandatory
> +	 */
> +	long (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
> +
> +	/**
> +	 * @get: Get the feature current value
> +	 *
> +	 * Return SBI_SUCCESS on success or an SBI error (SBI_ERR_*)
> +	 *
> +	 * This callback is mandatory
> +	 */
> +	 long (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);
        ^ 
	extra space here


Thanks,
drew