Re: [Qemu-devel] [PATCH v7 0/4] rng-builtin: add an RNG backend that uses qemu_guest_getrandom()

[Laurent Vivier]

On 05/06/2019 19:56, Markus Armbruster wrote:
> Laurent Vivier <address@hidden> writes:
> 
>> On 05/06/2019 15:05, Markus Armbruster wrote:
>>> Laurent Vivier <address@hidden> writes:
>>>
>>>> Add a new RNG backend using QEMU builtin getrandom function.
>>>>
>>>> v7: rebase on master
>>>>     Make rng-builtin asynchronous with QEMUBH (removed existing R-b)
>>>
>>> Pardon the ignorant question: why is that necessary?
>>>
>>
>> Because request_entropy() function is called while the request is not in
>> the requests queue, so the loop on !QSIMPLEQ_EMPTY(&s->parent.requests)
>> doens't process it. The request is added just after the call.
> 
> In rng_backend_request_entropy().  I see.  Any particular reason for
> this order?  "I don't know" is an acceptable answer :)
> 

Yes...

and there is a reason:

in rng_random_request_entropy(), QSIMPLEQ_EMPTY() is used to know if we
have to register an fd handler with qemu_set_fd_handler().

For me, it seemed easier to use QEMUBH rather than to change the
existing algorithm, as the backend has been thought to be asynchronous.

Thanks,
Laurent