Re: [PATCH] nvme-pci: Use non-operational power state instead of D3 on Suspend-to-Idle

From: Keith Busch
Date: Fri May 10 2019 - 10:08:59 EST

On Thu, May 09, 2019 at 11:05:42PM -0700, Kai-Heng Feng wrote:
> Yes, thatâ what I was told by the NVMe vendor, so all I know is to impose a
> memory barrier.
> If mb() shouldnât be used here, whatâs the correct variant to use in this
> context?

I'm afraid the requirement is still not clear to me. AFAIK, all our
barriers routines ensure data is visible either between CPUs, or between
CPU and devices. The CPU never accesses HMB memory, so there must be some
other reasoning if this barrier is a real requirement for this device.