From: John Levon <levon@movementarian.org>
To: Keith Busch <kbusch@kernel.org>
Cc: Klaus Jensen <its@irrelevant.dk>,
Jinhao Fan <fanjinhao21s@ict.ac.cn>,
qemu-devel@nongnu.org
Subject: Re: [PATCH 1/2] hw/nvme: Implement shadow doorbell buffer support
Date: Thu, 9 Jun 2022 16:52:02 +0100 [thread overview]
Message-ID: <YqIXIiQr+dpksBh6@movementarian.org> (raw)
In-Reply-To: <YqIDyjxrZnkeMfcE@kbusch-mbp.dhcp.thefacebook.com>
On Thu, Jun 09, 2022 at 08:29:30AM -0600, Keith Busch wrote:
> On Wed, Jun 08, 2022 at 10:55:30PM +0200, Klaus Jensen wrote:
> >
> > Keith, is this a bug in the kernel? If the code here would expect the
> > doorbell buffer to be updated for the admin queue as well, would we
> > break?
>
> The admin queue has to be created before db buffer can be set up, so we can't
> rely on it. And this is a performance feature. Admin commands have never been
> considered performant, so we decided not to consider it though the spec allows
> it.
It's not just unnecessary, but enabling shadow doorbells on admin queues will
actively break device implementations (such as SPDK), which have had to presume
that driver implementations don't use shadow doorbells for the admin queue.
regards
john
next prev parent reply other threads:[~2022-06-09 16:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-08 1:36 [PATCH 0/2] hw/nvme: Add shadow doorbell buffer support Jinhao Fan
2022-06-08 1:36 ` [PATCH 1/2] hw/nvme: Implement " Jinhao Fan
2022-06-08 20:55 ` Klaus Jensen
2022-06-09 1:49 ` Jinhao Fan
2022-06-09 14:29 ` Keith Busch
2022-06-09 15:52 ` John Levon [this message]
2022-06-09 17:27 ` Klaus Jensen
2022-06-09 17:50 ` John Levon
2022-06-12 11:40 ` Jinhao Fan
2022-06-13 21:15 ` Keith Busch
2022-06-14 7:24 ` Jinhao Fan
2022-06-14 15:41 ` Keith Busch
2022-06-15 3:58 ` Jinhao Fan
2022-06-15 9:38 ` Klaus Jensen
2022-06-15 14:52 ` Jinhao Fan
2022-06-15 8:48 ` Klaus Jensen
2022-06-15 9:07 ` John Levon
2022-06-15 9:33 ` Klaus Jensen
2022-06-15 10:11 ` John Levon
2022-06-15 11:22 ` Jinhao Fan
2022-06-15 11:45 ` John Levon
2022-06-08 1:36 ` [PATCH 2/2] hw/nvme: Add trace events for shadow doorbell buffer Jinhao Fan
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