Re: [PATCH v3 14/17] RISC-V: KVM: add SBI extension init()/deinit() functions

Andrew Jones
2025-03-13T14:27:20Z

On Mon, Mar 10, 2025 at 04:12:21PM +0100, Clément Léger wrote:
> The FWFT SBI extension will need to dynamically allocate memory and do
> init time specific initialization. Add an init/deinit callbacks that
> allows to do so.
>
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> ---
> arch/riscv/include/asm/kvm_vcpu_sbi.h | 9 +++++++++
> arch/riscv/kvm/vcpu.c | 2 ++
> arch/riscv/kvm/vcpu_sbi.c | 29 +++++++++++++++++++++++++++
> 3 files changed, 40 insertions(+)
>
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> index 4ed6203cdd30..bcb90757b149 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> @@ -49,6 +49,14 @@ struct kvm_vcpu_sbi_extension {
>
> /* Extension specific probe function */
> unsigned long (*probe)(struct kvm_vcpu *vcpu);
> +
> + /*
> + * Init/deinit function called once during VCPU init/destroy. These
> + * might be use if the SBI extensions need to allocate or do specific
> + * init time only configuration.
> + */
> + int (*init)(struct kvm_vcpu *vcpu);
> + void (*deinit)(struct kvm_vcpu *vcpu);
> };
>
> void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
> @@ -69,6 +77,7 @@ const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
> 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);
>
> 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 60d684c76c58..877bcc85c067 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -185,6 +185,8 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
>
> void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
> {
> + kvm_riscv_vcpu_sbi_deinit(vcpu);
> +
> /* Cleanup VCPU AIA context */
> kvm_riscv_vcpu_aia_deinit(vcpu);
>
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index d1c83a77735e..858ddefd7e7f 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -505,8 +505,37 @@ void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu)
> continue;
> }
>
> + if (!ext->default_disabled && ext->init &&
> + ext->init(vcpu) != 0) {
> + scontext->ext_status[idx] = KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
> + continue;
> + }

I think this new block should be below the assignment below (and it can
drop the continue) and it shouldn't check default_disabled (as I've done
below). IOW, we should always run ext->init when there is one to run here.
Otherwise, I how will it get run later?

> +
> scontext->ext_status[idx] = ext->default_disabled ?
> KVM_RISCV_SBI_EXT_STATUS_DISABLED :
> KVM_RISCV_SBI_EXT_STATUS_ENABLED;

if (ext->init && ext->init(vcpu))
scontext->ext_status[idx] = KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;

> }
> }
> +
> +void kvm_riscv_vcpu_sbi_deinit(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_UNAVAILABLE ||
> + !ext->deinit)
> + continue;
> +
> + ext->deinit(vcpu);
> + }
> +}
> --
> 2.47.2
>

Thanks,
drew