[PATCH] nvme-pci: Remove O2 Queue Depth quirk

[Keith Busch]

On Tue, Oct 29, 2024 at 11:58:40AM -0700, Gwendal Grignou wrote:
> On Tue, Oct 29, 2024 at 12:41 AM Christoph Hellwig <hch at lst.de> wrote:
> >
> > On Mon, Oct 28, 2024 at 07:42:36PM -0700, Gwendal Grignou wrote:
> > > PCI_DEVICE(0x1217, 0x8760) (O2 Micro, Inc. FORESEE E2M2 NVMe SSD)
> > > is a NMVe to eMMC bridge, that can be used with different eMMC
> > > memory devices.
> >
> > Holy f**k, what an awful idea..
> >
> > > The NVMe device name contains the eMMC device name, for instance:
> > > `BAYHUB SanDisk-DA4128-91904055-128GB`
> > >
> > > The bridge is known to work with many eMMC devices, we need to limit
> > > the queue depth once we know which eMMC device is behind the bridge.
> >
> > Please work with Tobert to quirk based on the identify data for "his"
> > device to keep it quirked instead of regressing it.
> 
> The issue is we would need to base the quirk on the model name
> (subsys->model) that is not available in `nvme_id_table`. Beside,
> `q_depth` is set in `nvme_pci_enable`, called at probe time before
> calling `nvme_init_ctrl_finish` that will indirectly populate
> `subsys`.
> 
> Bob, to address the data corruption problem from user space, adding a
> udev rule to set `queue/nr_requests` to 1 when `device/model` matches
> the device used in the Steam Deck would most likely be too late in the
> boot process, wouldn't it?

I think that is too late. There's the module parameter,
'nvme.io_queue_depth=2', that accomplishes the same thing as this quirk,
if adding kernel parameters isn't too inconvenient to use here.

Alternatively, you could put the quirk in the core_quirks, which do take
a model name. The pci driver would have to move this check until after
init_ctrl_finish, as you noticed, but that looks okay to do. We just
need to be careful to update both dev->q_depth and ctrl->sqsize after
the "finish".