Re: [PATCH v6 12/14] RISC-V: KVM: add SBI extension reset callback

[Atish Patra <atish.patra@linux.dev>]

On 4/24/25 10:31 AM, Clément Léger wrote:
> Currently, only the STA extension needed a reset function but that's
> going to be the case for FWFT as well. Add a reset callback that can be
> implemented by SBI extensions.
> 
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>   arch/riscv/include/asm/kvm_host.h     |  1 -
>   arch/riscv/include/asm/kvm_vcpu_sbi.h |  2 ++
>   arch/riscv/kvm/vcpu.c                 |  2 +-
>   arch/riscv/kvm/vcpu_sbi.c             | 24 ++++++++++++++++++++++++
>   arch/riscv/kvm/vcpu_sbi_sta.c         |  3 ++-
>   5 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 0e9c2fab6378..4fa02e082142 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -407,7 +407,6 @@ void __kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
>   void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
>   bool kvm_riscv_vcpu_stopped(struct kvm_vcpu *vcpu);
>   
> -void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu);
>   void kvm_riscv_vcpu_record_steal_time(struct kvm_vcpu *vcpu);
>   
>   #endif /* __RISCV_KVM_HOST_H__ */
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> index bcb90757b149..cb68b3a57c8f 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> @@ -57,6 +57,7 @@ struct kvm_vcpu_sbi_extension {
>   	 */
>   	int (*init)(struct kvm_vcpu *vcpu);
>   	void (*deinit)(struct kvm_vcpu *vcpu);
> +	void (*reset)(struct kvm_vcpu *vcpu);
>   };
>   
>   void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
> @@ -78,6 +79,7 @@ bool riscv_vcpu_supports_sbi_ext(struct kvm_vcpu *vcpu, int idx);
>   int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);
>   void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
>   void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
> +void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu);
>   
>   int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
>   				   unsigned long *reg_val);
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 877bcc85c067..542747e2c7f5 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -94,7 +94,7 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
>   	vcpu->arch.hfence_tail = 0;
>   	memset(vcpu->arch.hfence_queue, 0, sizeof(vcpu->arch.hfence_queue));
>   
> -	kvm_riscv_vcpu_sbi_sta_reset(vcpu);
> +	kvm_riscv_vcpu_sbi_reset(vcpu);
>   
>   	/* Reset the guest CSRs for hotplug usecase */
>   	if (loaded)
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index 3139f171c20f..50be079b5528 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -536,3 +536,27 @@ void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu)
>   		ext->deinit(vcpu);
>   	}
>   }
> +
> +void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
> +	const struct kvm_riscv_sbi_extension_entry *entry;
> +	const struct kvm_vcpu_sbi_extension *ext;
> +	int idx, i;
> +
> +	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
> +		entry = &sbi_ext[i];
> +		ext = entry->ext_ptr;
> +		idx = entry->ext_idx;
> +
> +		if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
> +			continue;
> +
> +		if (scontext->ext_status[idx] != KVM_RISCV_SBI_EXT_STATUS_ENABLED ||
> +		    !ext->reset)
> +			continue;
> +
> +		ext->reset(vcpu);
> +	}
> +}
> +
> diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
> index 5f35427114c1..cc6cb7c8f0e4 100644
> --- a/arch/riscv/kvm/vcpu_sbi_sta.c
> +++ b/arch/riscv/kvm/vcpu_sbi_sta.c
> @@ -16,7 +16,7 @@
>   #include <asm/sbi.h>
>   #include <asm/uaccess.h>
>   
> -void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu)
> +static void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu)
>   {
>   	vcpu->arch.sta.shmem = INVALID_GPA;
>   	vcpu->arch.sta.last_steal = 0;
> @@ -156,6 +156,7 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {
>   	.extid_end = SBI_EXT_STA,
>   	.handler = kvm_sbi_ext_sta_handler,
>   	.probe = kvm_sbi_ext_sta_probe,
> +	.reset = kvm_riscv_vcpu_sbi_sta_reset,
>   };
>   
>   int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu,

LGTM.
Reviewed-by: Atish Patra <atishp@rivosinc.com>