Re: Re: [PATCH v7 1/4] RISC-V: KVM: Support runtime configuration for per-VM's HGATP mode

[fangyu . yu]

>> From: Fangyu Yu <fangyu.yu@xxxxxxxxxxxxxxxxx>
>>
>> Introduces one per-VM architecture-specific fields to support runtime
>> configuration of the G-stage page table format:
>>
>> - kvm->arch.pgd_levels: the corresponding number of page table levels
>>   for the selected mode.
>>
>> These fields replace the previous global variables
>> kvm_riscv_gstage_mode and kvm_riscv_gstage_pgd_levels, enabling different
>> virtual machines to independently select their G-stage page table format
>> instead of being forced to share the maximum mode detected by the kernel
>> at boot time.
>>
>> Signed-off-by: Fangyu Yu <fangyu.yu@xxxxxxxxxxxxxxxxx>
>> Reviewed-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>
>> Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
>> Reviewed-by: Guo Ren <guoren@xxxxxxxxxx>
>> ---
>> diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
>> @@ -199,7 +199,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>>  		r = KVM_USER_MEM_SLOTS;
>>  		break;
>>  	case KVM_CAP_VM_GPA_BITS:
>> -		r = kvm_riscv_gstage_gpa_bits;
>> +		r = kvm_riscv_gstage_gpa_bits(kvm->arch.pgd_levels);
>
>kvm_vm_ioctl_check_extension() also gets called from with kvm == NULL
>from kvm_dev_ioctl().  I think we can continue to return
>...(kvm_riscv_gstage_max_pgd_levels) in that case.
>

Thanks for catching this. I’ll handle the kvm == NULL case (from kvm_dev_ioctl)
and return the host maximum based on kvm_riscv_gstage_max_pgd_levels in v8.

Also, if the intended semantics of KVM_CAP_VM_GPA_BITS is to report the maximum
supported value, then we could simply always return the host maximum based on
kvm_riscv_gstage_max_pgd_levels.

Thanks,
Fangyu

>Thanks.