linux-kernel - Re: [PATCH V2 2/2] virtio_pmem: set device ready in probe()

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Date:   Mon, 27 Jun 2022 06:03:17 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        linux-kernel <linux-kernel@...r.kernel.org>, pankaj.gupta@....com
Subject: Re: [PATCH V2 2/2] virtio_pmem: set device ready in probe()

On Mon, Jun 27, 2022 at 04:34:07PM +0800, Jason Wang wrote:
> On Mon, Jun 27, 2022 at 4:00 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > On Mon, Jun 27, 2022 at 02:29:41PM +0800, Jason Wang wrote:
> > > The NVDIMM region could be available before the virtio_device_ready()
> > > that is called by virtio_dev_probe(). This means the driver tries to
> > > use device before DRIVER_OK which violates the spec, fixing this by
> >
> > s/fixing this by/to fix this/
> >
> > > set device ready before the nvdimm_pmem_region_create().
> > >
> > > Note that this means the virtio_pmem_host_ack() could be triggered
> > > before the creation of the nd region, this is safe since the
> > > virtio_pmem_host_ack() since pmem_lock has been initialized and
> >
> > can't parse this sentence, since repeated twice confuses me
> 
> Should be a copy-paste error: how about:
> 
> Note that this means the virtio_pmem_host_ack() could be triggered
> before the creation of the nd region, this is safe since the pmem_lock
> has been initialized and whether or not any available buffer is added
> before is validated by virtio_pmem_host_ack().
> 
> Thanks

looks good

> >
> > > whether or not any available buffer is added before is validated.
> > >
> > > Fixes 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
> > > Acked-by: Pankaj Gupta <pankaj.gupta@....com>
> > > Signed-off-by: Jason Wang <jasowang@...hat.com>
> > > ---
> > > Changes since v1:
> > > - Remove some comments per Dan
> > > ---
> > >  drivers/nvdimm/virtio_pmem.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >
> > > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> > > index 48f8327d0431..20da455d2ef6 100644
> > > --- a/drivers/nvdimm/virtio_pmem.c
> > > +++ b/drivers/nvdimm/virtio_pmem.c
> > > @@ -84,6 +84,12 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
> > >       ndr_desc.provider_data = vdev;
> > >       set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
> > >       set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
> > > +     /*
> > > +      * The NVDIMM region could be available before the
> > > +      * virtio_device_ready() that is called by
> > > +      * virtio_dev_probe(), so we set device ready here.
> > > +      */
> > > +     virtio_device_ready(vdev);
> > >       nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
> > >       if (!nd_region) {
> > >               dev_err(&vdev->dev, "failed to create nvdimm region\n");
> > > @@ -92,6 +98,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
> > >       }
> > >       return 0;
> > >  out_nd:
> > > +     virtio_reset_device(vdev);
> > >       nvdimm_bus_unregister(vpmem->nvdimm_bus);
> > >  out_vq:
> > >       vdev->config->del_vqs(vdev);
> > > --
> > > 2.25.1
> >