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Re: [PATCH v6 09/42] nvme: add max_ioqpairs device parameter
From: |
Klaus Birkelund Jensen |
Subject: |
Re: [PATCH v6 09/42] nvme: add max_ioqpairs device parameter |
Date: |
Tue, 31 Mar 2020 07:40:10 +0200 |
On Mar 25 12:39, Maxim Levitsky wrote:
> On Mon, 2020-03-16 at 07:28 -0700, Klaus Jensen wrote:
> > From: Klaus Jensen <address@hidden>
> >
> > The num_queues device paramater has a slightly confusing meaning because
> > it accounts for the admin queue pair which is not really optional.
> > Secondly, it is really a maximum value of queues allowed.
> >
> > Add a new max_ioqpairs parameter that only accounts for I/O queue pairs,
> > but keep num_queues for compatibility.
> >
> > Signed-off-by: Klaus Jensen <address@hidden>
> > ---
> > hw/block/nvme.c | 45 ++++++++++++++++++++++++++-------------------
> > hw/block/nvme.h | 4 +++-
> > 2 files changed, 29 insertions(+), 20 deletions(-)
> >
> > diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> > index 7cf7cf55143e..7dfd8a1a392d 100644
> > --- a/hw/block/nvme.c
> > +++ b/hw/block/nvme.c
> > @@ -1332,9 +1333,15 @@ static void nvme_realize(PCIDevice *pci_dev, Error
> > **errp)
> > int64_t bs_size;
> > uint8_t *pci_conf;
> >
> > - if (!n->params.num_queues) {
> > - error_setg(errp, "num_queues can't be zero");
> > - return;
> > + if (n->params.num_queues) {
> > + warn_report("nvme: num_queues is deprecated; please use
> > max_ioqpairs "
> > + "instead");
> > +
> > + n->params.max_ioqpairs = n->params.num_queues - 1;
> > + }
> > +
> > + if (!n->params.max_ioqpairs) {
> > + error_setg(errp, "max_ioqpairs can't be less than 1");
> > }
> This is not even a nitpick, but just and idea.
>
> It might be worth it to allow max_ioqpairs=0 to simulate a 'broken'
> nvme controller. I know that kernel has special handling for such controllers,
> which include only creation of the control character device (/dev/nvme*)
> through
> which the user can submit commands to try and 'fix' the controller (by
> re-uploading firmware
> maybe or something like that).
>
>
Not sure about the implications of this, so I'll leave that on the TODO
:) But a controller with no I/O queues is an "Administrative Controller"
and perfectly legal in NVMe v1.4 AFAIK.
> >
> > if (!n->conf.blk) {
> > @@ -1365,19 +1372,19 @@ static void nvme_realize(PCIDevice *pci_dev, Error
> > **errp)
> > pcie_endpoint_cap_init(pci_dev, 0x80);
> >
> > n->num_namespaces = 1;
> > - n->reg_size = pow2ceil(0x1004 + 2 * (n->params.num_queues + 1) * 4);
> > + n->reg_size = pow2ceil(0x1008 + 2 * (n->params.max_ioqpairs) * 4);
>
> I hate to say it, but it looks like this thing (which I mentioned to you in
> V5)
> was pre-existing bug, which is indeed fixed now.
> In theory such fixes should go to separate patches, but in this case, I guess
> it would
> be too much to ask for it.
> Maybe mention this in the commit message instead, so that this fix doesn't
> stay hidden like that?
>
>
I'm convinced now. I have added a preparatory bugfix patch before this
patch.
>
> Reviewed-by: Maxim Levitsky <address@hidden>
>
> Best regards,
> Maxim Levitsky
>
[PATCH v6 16/42] nvme: make sure ncqr and nsqr is valid, Klaus Jensen, 2020/03/16
[PATCH v6 14/42] nvme: add missing mandatory features, Klaus Jensen, 2020/03/16