Re: [PATCH v2 5/9] nvme: Fix invalid call toirq_set_affinity_hint()

[Keith Busch]

On Fri, 17 Jan 2014, Bjorn Helgaas wrote:

> On Fri, Jan 17, 2014 at 9:02 AM, Alexander Gordeev <agordeev@xxxxxxxxxx> wrote:
> > In case MSI-X and MSI initialization failed the function
> > irq_set_affinity_hint() is called with uninitialized value
> > in dev->entry[0].vector. This update fixes the issue.
>
> dev->entry[0].vector is initialized in nvme_dev_map(), and it's used
> for free_irq() above the area of your patch, so I don't think this is
> actually a bug, though it might be somewhat confusing.

It is confusing, but there's a reason. :)

We send a single command using legacy irq to discover how many msix
vectors we want. The legacy entry needs to be set some time before calling
request_irq in nvme_configure_admin_queue, but also within nvme_dev_start
(for power-management). I don't think there's a place to set it that
won't look odd when looking at nvme_setup_io_queues. I settled on
'nvme_dev_map' was because 'nvme_dev_unmap' invalidates the entries,
so this seemed to provide some amount of symmetry.

> > Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
> > ---
> >  drivers/block/nvme-core.c |   12 ++++++------
> >  1 files changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> > index 26d03fa..e292450 100644
> > --- a/drivers/block/nvme-core.c
> > +++ b/drivers/block/nvme-core.c
> > @@ -1790,15 +1790,15 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
> >                         vecs = 32;
> >                 for (;;) {
> >                         result = pci_enable_msi_block(pdev, vecs);
> > -                       if (result == 0) {
> > -                               for (i = 0; i < vecs; i++)
> > -                                       dev->entry[i].vector = i + pdev->irq;
> > -                               break;
> > +                       if (result > 0) {
> > +                               vecs = result;
> > +                               continue;
> >                         } else if (result < 0) {
> >                                 vecs = 1;
> > -                               break;
> >                         }
> > -                       vecs = result;
> > +                       for (i = 0; i < vecs; i++)
> > +                               dev->entry[i].vector = i + pdev->irq;
> > +                       break;
> >                 }
> >         }
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