From mboxrd@z Thu Jan 1 00:00:00 1970 From: keith.busch@intel.com (Keith Busch) Date: Mon, 5 Aug 2019 07:49:07 -0600 Subject: [PATCH v3] nvme-pci: Support shared tags across queues for Apple 2018 controllers In-Reply-To: <6290507e1b2830b1729fc858cd5c20b85d092728.camel@kernel.crashing.org> References: <20190730153044.GA13948@localhost.localdomain> <2030a028664a9af9e96fffca3ab352faf1f739e5.camel@kernel.crashing.org> <6290507e1b2830b1729fc858cd5c20b85d092728.camel@kernel.crashing.org> Message-ID: <20190805134907.GC18647@localhost.localdomain> On Mon, Aug 05, 2019@04:49:23PM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2019-07-30@13:28 -0700, Benjamin Herrenschmidt wrote: > > > One problem is that we've an nvme parameter, io_queue_depth, that a user > > > could set to something less than 32, and then you won't be able to do > > > any IO. I'd recommend enforce the admin queue to QD1 for this device so > > > that you have more potential IO tags. > > > > So I had a look and it's not that trivial. I would have to change > > a few things that use constants for the admin queue depth, such as > > the AEN tag etc... > > > > For such a special case, I am tempted instead to do the much simpler: > > > > if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS) { > > if (dev->q_depth < (NVME_AQ_DEPTH + 2)) > > dev->q_depth = NVME_AQ_DEPTH + 2; > > } > > > > In nvme_pci_enable() next to the existing q_depth hackery for other > > controllers. > > > > Thoughts ? > > Ping ? I had another look today and I don't feel like mucking around > with all the AQ size logic, AEN magic tag etc... just for that sake of > that Apple gunk. I'm happy to have it give up IO tags, it doesn't seem > to make much of a difference in practice anyway. > > But if you feel strongly about it, then I'll implement the "proper" way > sometimes this week, adding a way to shrink the AQ down to something > like 3 (one admin request, one async event (AEN), and the empty slot) > by making a bunch of the constants involved variables instead. I don't feel too strongly about it. I think your patch is fine, so Acked-by: Keith Busch