Re: [PATCH] nvme/pci: Use host managed power state for suspend

From: Keith Busch
Date: Mon May 13 2019 - 11:23:51 EST

On Mon, May 13, 2019 at 04:57:08PM +0200, Christoph Hellwig wrote:
> On Mon, May 13, 2019 at 02:54:49PM +0000, Mario.Limonciello@xxxxxxxx wrote:
> > And NVME spec made it sound to me that while in a low power state it shouldn't
> > be available if the memory isn't available.
> >
> > NVME spec in 8.9:
> >
> > "Host software should request that the controller release the
> > assigned ranges prior to a shutdown event, a Runtime D3 event, or any other event
> > that requires host software to reclaim the assigned ranges."
> The last part of the quoted text is the key - if the assigned range
> is reclaimed, that is the memory is going to be used for something else,
> we need to release the ranges. But we do not release the ranges,
> as we want to keep the memory in use so that we can quickly use it
> again.

Yes, this. As far as I know, the host memory range is still accessible in
the idle suspend state. If there are states in which host memory is not
accessible, a reference explaining the requirement will be most helpful.