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Date:      Tue, 28 May 2019 11:19:07 -0700
From:      Colin Percival <cperciva@freebsd.org>
To:        Andriy Gapon <avg@FreeBSD.org>, Warner Losh <imp@bsdimp.com>, Matthew Seaman <matthew@freebsd.org>
Cc:        "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, Alex Dupre <ale@freebsd.org>, Jonathan Anderson <jonathan@freebsd.org>
Subject:   Re: Amazon AMIs
Message-ID:  <79d5cdad-3a95-de88-25ee-0dd8d27a442e@freebsd.org>
In-Reply-To: <74ed9ad5-58d9-db02-2e20-b053ba5eeb87@FreeBSD.org>
References:  <f002c020-1e63-c12f-456e-e20f8546a701@FreeBSD.org> <8a139c9c-b98b-4a54-1d7c-0ea1e3dc7a72@freebsd.org> <53a0bd68-a6ba-e8ad-4af2-abeb22e92c03@FreeBSD.org> <E396A0C7-F939-48A1-9B57-D643806B303B@FreeBSD.org> <f51b836f-6a40-9be3-425a-e1afd301507b@FreeBSD.org> <CANCZdfp0ZWe11jXw_xnPi8G2QhyEeBTOcN_ks=sqJCqDjDYcQg@mail.gmail.com> <74ed9ad5-58d9-db02-2e20-b053ba5eeb87@FreeBSD.org>

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On 5/28/19 5:52 AM, Andriy Gapon wrote:
> On 21/02/2019 18:17, Warner Losh wrote:
>> 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.

Right, these EC2 instances look like they have NVMe devices being hotplugged
on a legacy PCI bus attached to an Intel 440FX chipset.  There is no real
hardware which behaves the same way as these VMs.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid



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