Re: [libvirt] [PATCH v5 06/13] conf: Introduce address caching for PCI extensions
在 2018/9/12 下午6:37, Andrea Bolognani 写道:
On Wed, 2018-09-12 at 16:34 +0800, Yi Min Zhao wrote:
> 在 2018/9/12 下午3:35, Yi Min Zhao 写道:
>>> This makes sense and seems to work just fine; however, you are
>>> allocating and releasing a bunch of small integers, which seems
>>> a bit wasteful.
>>>
>>> vircgroup is AFAICT avoiding all that extra memory management by
>>> stuffing the values straight into the pointers themselves, which
>>> you should also be able to do since the biggest legal ID is a
>>> 32-bit integer.
>>>
>>> That said, I haven't been able to get that to actually work, at
>>> least with a quick attempt :( Would you mind exploring that route
>>> and figuring out whether it's feasible at all?
>> I'm testing this. Actually I wanted to do so like vircgroup. I
>> remembered there's
>> error due to the previous code logic. I will reply to you later.
> I remebered the reason and test again. FID might be 0. It is treated as
> an error
> if we save 0 in void* pointer.
Right.
Too bad fid can go all the way to UINT32_MAX, otherwise we could
have just stored them in the pointer after offsetting them by one
and thus worked around the issue...
Yes. Just one value makes all things complex.
I guess forbidding users from using UINT32_MAX as a fid is not an
option, right?
Actually as my understanding, it's just a value to identify the pci
function.
IMO, it's not a big deal to decrease usable FID values. After all, UID set
is smaller than FID set. The maximum number of pci devices is limited
by UID. Anyway, I have to discuss this with my colleagues internally.
I will tell you our discussion result first time.
--
Yi Min