Re: [PATCH] spapr: Add "memop" hypercall

Alexander Graf
2012-05-30T08:25:59Z

On 28.05.2012, at 12:40, Avi Kivity wrote:

> On 05/25/2012 06:12 AM, Benjamin Herrenschmidt wrote:
>>
>> BTW. This is a qemu patch, and that hypercall isn't KVM related at all,
>> ie, it's implemented in qemu and is used with or without KVM, so
>> documenting it in the kernel tree makes little sense. Same goes with
>> H_RTAS.
>>
>> I'll add a doc to qemu in my next spin of it.
>>
>
> Depends. How do you detect it exists? Are you detecting kvm, or qemu,
> or the hypercall itself?

The hypercall itself. SLOF is the only user. QEMU provides SLOF. SLOF calls the hypercall. If the hypercall returns "I don't exist", it doesn't exist. :)

> I'd hate us to find ourselves in a maze of disconnected documentation
> with no clear guidelines on when a feature is available and when it is not.

Yeah, but semantically these hypercalls are on the same layer as fw_cfg. So they clearly belong to QEMU. In fact, they're also used when running with emulation.

Alex