Re: [PATCH 2/2] NVMe: Implement PCI-e reset notification callback

[Learner Study <learner.study@gmail.com>]

It would be interesting to see which way the standard open source
driver decides to go...would we allow Reset in one VF to impact
operations in other VFs (as per spec 7.3.1 of NVMe 1.1 spec, "When an
NVM Subsystem Reset occurs, the entire NVM subsystem is reset"...)

On Mon, Apr 21, 2014 at 10:02 PM, Mayes, Barrett N
<barrett.n.mayes@intel.com> wrote:
> Section 8.5 of the NVMe 1.1 spec contains the following:  "While the details associated with implementing a controller that supports SR-IOV are outside the scope of this specification, such a controller shall implement fully compliant NVM Express Virtual Functions (VFs). This ensures that the same host software developed for non-virtualized environments is capable of running unmodified within an SI. No such requirement exists for the Physical Function (PF)."
>
> If a VF is a fully NVMe compliant device then it must at least act like it implements NVMe subsystem reset.  How the SR-IOV-capable controller actually implements this is left up to the vendor.  But the spec does not require that a reset of one VF initiate a reset of other VF.
>
> -----Original Message-----
> From: Linux-nvme [mailto:linux-nvme-bounces@lists.infradead.org] On Behalf Of Learner Study
> Sent: Monday, April 21, 2014 8:34 PM
> To: Busch, Keith
> Cc: bhelgaas@google.com; linux-pci@vger.kernel.org; linux-nvme
> Subject: Re: [PATCH 2/2] NVMe: Implement PCI-e reset notification callback
>
> Per the spec, "When an NVM Subsystem Reset occurs, the entire NVM subsystem is reset"....so all VFs would get impacted, if a VF does a Reset. So, I think Reset kind of control should be in PF mode only.
>
> On Mon, Apr 21, 2014 at 7:45 PM, Learner <learner.study@gmail.com> wrote:
>> But Won't resetting from a VF impact functionality of other VFs?
>>
>> On Apr 21, 2014, at 6:57 PM, Keith Busch <keith.busch@intel.com> wrote:
>>
>>> On Mon, 21 Apr 2014, Learner Study wrote:
>>>> Hi Keith,
>>>>
>>>> I think NVMe Reset should apply to PF mode driver only, and not to
>>>> VF mode driver.
>>>> Is that understanding correct? Does the NVMe driver know which mode
>>>> its running in?
>>>
>>> Oh, this driver doesn't enable SR-IOV and has no PF/VF awareness.
>>> Shame on us, I'll add it to my list unless someone beats me to it.
>>>
>>> Still, I think we'd like to be able to reset a VF if only because it
>>> gets the queues back to a pristine state. A VF reset should not
>>> affect any of the other functions.
>
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