Re: [RFC 2/5] selftests: KVM: Decouple SEV ioctls from asserts

["Pratik R. Sampat" <pratikrajesh.sampat@amd.com>]

On 8/13/2024 10:27 AM, Sean Christopherson wrote:
> On Tue, Aug 13, 2024, Pratik R. Sampat wrote:
>> On 8/9/2024 10:40 AM, Sean Christopherson wrote:
>>> On Wed, Jul 10, 2024, Pratik R. Sampat wrote:
>>>> @@ -98,7 +100,7 @@ static inline void sev_register_encrypted_memory(struct kvm_vm *vm,
>>>>  	vm_ioctl(vm, KVM_MEMORY_ENCRYPT_REG_REGION, &range);
>>>>  }
>>>>  
>>>> -static inline void snp_launch_update_data(struct kvm_vm *vm, vm_paddr_t gpa,
>>>> +static inline int snp_launch_update_data(struct kvm_vm *vm, vm_paddr_t gpa,
>>>>  					   uint64_t size, uint8_t type)
>>>>  {
>>>>  	struct kvm_sev_snp_launch_update update_data = {
>>>> @@ -108,10 +110,10 @@ static inline void snp_launch_update_data(struct kvm_vm *vm, vm_paddr_t gpa,
>>>>  		.type = type,
>>>>  	};
>>>>  
>>>> -	vm_sev_ioctl(vm, KVM_SEV_SNP_LAUNCH_UPDATE, &update_data);
>>>> +	return __vm_sev_ioctl(vm, KVM_SEV_SNP_LAUNCH_UPDATE, &update_data);
>>>
>>> Don't introduce APIs and then immediately rewrite all of the users.  If you want
>>> to rework similar APIs, do the rework, then add the new APIs.  Doing things in
>>> this order adds a pile of pointless churn.
>>>
>>> But that's a moot point, because it's far easier to just add __snp_launch_update_data().
>>> And if you look through other APIs in kvm_util.h, you'll see that the strong
>>> preference is to let vm_ioctl(), or in this case vm_sev_ioctl(), do the heavy
>>> lifting.  Yeah, it requires copy+pasting marshalling parameters into the struct,
>>> but that's relatively uninteresting code, _and_ piggybacking the "good" version
>>> means you can't do things like pass in a garbage virtual address (because the
>>> "good" version always guarantees a good virtual address).
>>
>> I am a little confused by this.
>>
>> Are you suggesting that I leave the original functions intact with using
>> vm_sev_ioctl() and have an additional variant such as
>> __snp_launch_update_data() which calls into __vm_sev_ioctl() to decouple
>> the ioctl from the assert for negative asserts?
> 
> Yes, this one.

Got it. Thanks a lot!

> 
>> Or, do you suggest that I alter vm_sev_ioctl() to handle both positive
>> and negative asserts?
>>
>> Thanks!
>> -Pratik
>>