From: John Levon <levon@movementarian.org>
To: Keith Busch <kbusch@kernel.org>
Cc: linux-nvme@lists.infradead.org, hch@lst.de, sagi@grimberg.me
Subject: Re: [PATCHv2 2/2] nvme-pci: remove cached shadow doorbell offsets
Date: Thu, 14 Oct 2021 18:09:30 +0100 [thread overview]
Message-ID: <YWhkSnjjTo3YioC+@movementarian.org> (raw)
In-Reply-To: <20211014164543.1821327-3-kbusch@kernel.org>
On Thu, Oct 14, 2021 at 09:45:43AM -0700, Keith Busch wrote:
> And when this feature is in use, the specification requires all queue
> updates use this mechanism, so don't don't treat the admin queue
> differently.
Hi Keith, I think you might have missed the other email from me?
This would cause implementation difficulties for a controller, right?
Currently we presume that the admin queue's shadow doorbells aren't valid, so
always look at the BAR0 location. Given we need to support older Linux versions,
we don't have any non-hacky way to handle this: we'd need something horrible
that presumes those Linux versions - and any other driver implementations -
always leave the admin queue shadows at zero, so if we see a non-zero value, it
must be doing shadow doorbells.
It's unclear to me what the advantage of fixing this is, given Linux has been
out of spec for so long.
regards
john
next prev parent reply other threads:[~2021-10-14 17:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-14 16:45 [PATCHv2 0/2] nvme shadow doorbel buf fixes Keith Busch
2021-10-14 16:45 ` [PATCHv2 1/2] nvme-pci: clear shadow doorbell memory on resets Keith Busch
2021-10-14 21:21 ` John Levon
2021-10-20 17:23 ` Christoph Hellwig
2021-10-14 16:45 ` [PATCHv2 2/2] nvme-pci: remove cached shadow doorbell offsets Keith Busch
2021-10-14 16:53 ` Christoph Hellwig
2021-10-14 17:09 ` John Levon [this message]
2021-10-14 17:49 ` Keith Busch
2021-10-14 18:33 ` John Levon
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