[PATCH] nvme-pci: fix host memory buffer allocation size

[Thomas Weißschuh]

On 2022-05-10 12:20+0200, Thomas Weißschuh wrote:
> [..]
> > We could look into removing the min with
> > PAGE_SIZE * MAX_ORDER_NR_PAGES to try to do larger segments for
> > "segment challenged" controllers now that it could work on a lot
> > of iommu enabled setups.  But I'd rather have a very good reason for
> > that.
> 
> On my current setup (WD SN770 on ThinkPad X1 Carbon Gen9) frequently the NVME
> controller stops responding. Switching from no scheduler to mq-deadline reduced
> this but did not eliminate it.
> Since switching to HMB of 1 * 200MiB and no scheduler this did not happen anymore.
> (But I'll need some more time to gain real confidence in this)

So this patch dramatically improves the stability of my disk.

Without it and queue/scheduler=none the controller stops responding after a few
minutes. mq-deadline reduced it to every few hours.

With the patch it happens roughly once a week.

I'll still RMA the disk and see if the replacement changes anything.

Maybe some of the Western Digital employees here could take a look or check if
there is a new firmware available.
(The official updater requires Windows and there is no external documentation
about the firmware)

Not sure if a change from very broken to only slightly broken would be enough
of a good reason to be honest.

Thomas