Re: [PATCH v8 13/14] RISC-V: KVM: add support for FWFT SBI extension

[Clément Léger]

On 23/05/2025 15:05, Radim Krčmář wrote:
> 2025-05-23T12:19:30+02:00, Clément Léger <cle...@rivosinc.com>:
>> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
>> +static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
>> +    SBI_FWFT_MISALIGNED_EXC_DELEG,
>> +    SBI_FWFT_LANDING_PAD,
>> +    SBI_FWFT_SHADOW_STACK,
>> +    SBI_FWFT_DOUBLE_TRAP,
>> +    SBI_FWFT_PTE_AD_HW_UPDATING,
>> +    SBI_FWFT_POINTER_MASKING_PMLEN,
>> +};
> 
> How will userspace control which subset of these features is allowed in
> the guest?
> 
> (We can reuse the KVM SBI extension interface if we don't want to add a
>  FWFT specific ONE_REG.)

Hi Radim,

I didn't looked at that part. But most likely using the kvm one reg
interface seems ok like what is done for STA ? We could have per feature
override with one reg per feature.

Is this something blocking though ? We'd like to merge FWFT once SBI 3.0
is ratified so that would be nice not delaying it too much. I'll take a
look at it to see if it isn't too long to implement.

Thanks,

Clément

> 
> Thanks.