Amazon AMIs

[Andriy Gapon]

On 21/02/2019 18:17, Warner Losh wrote:
> On Thu, Feb 21, 2019 at 1:02 AM Matthew Seaman <matthew at freebsd.org> wrote:
> 
>> On 20/02/2019 22:32, Jonathan Anderson wrote:
>>> On 20 Feb 2019, at 18:50, Alex Dupre wrote:
>>>
>>>> Colin Percival wrote:
>>>>> Last time I looked at this, we weren't handling hotplug/hotunplug of
>>>>> "NVMe"
>>>>> disks properly on the m5/c5/etc. instances.  I opted to recommend the
>>>>> instance
>>>>> which completely works rather than the one with slightly better
>>>>> performance...
>>>>
>>>> It does happen only on a few instances, but I get some freezes on new t3
>>>> machines: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=235856
>>>>
>>>> They are indeed cheaper and more performant, but not 100% reliable in
>>>> every workload.
>>>
>>> https://www.xkcd.com/937 ?
>>>
>>
>> Yes, indeed.  That's a very good reason not to recommend the newest and
>> shiniest.  I haven't seen any problems so far, but then again it's only
>> been a day or so and we haven't got into the full testing regime quite
>> yet.  I'll let you know if we do run into problems.
>>
>> Is there work on hot-plug NVMe going on?  ISTR jmg@ mentioning hotplug
>> PCI at the dev summit at Stockholm EuroBSDCon, but not much since then.
>>
> 
> It's hot-unplug that doesn't work quite right. Hotplug works, I believe, if
> you have PCI_HP in your kernel, I believe.
> 
> What's needed is about a solid week of cleanup and testing in this area,
> however.

I am not sure about the context of the latest question... whether it was about
NVMe hot-plug on real modern hardware or whether it was still about AWS.
In the latter case, as Colin pointed out earlier[*], PCI_HP would not help at
all, because the emulated bridge is not a PCIe bridge.
It seems that they use a mechanism based on an older specification, PCI Standard
Hot-Plug Controller and Subsystem Specification.
I believe that FreeBSD never implemented it.

[*] http://www.daemonology.net/blog/2017-11-17-FreeBSD-EC2-C5-instances.html

-- 
Andriy Gapon