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

Clément Léger
2025-03-14T13:54:01Z

On 13/03/2025 15:27, Andrew Jones wrote:
> 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?

Ok, i did not saw that there was a possibility to enable the extension
at a later time. I'll fix that.

Thanks,

Clément

>
>> +
>> 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