linux-kernel - Re: [PATCH v1] virtio-pci: Fix legacy device flag setting error in probe

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Message-ID: <CACGkMEuk2aBhnViZkAi8tbNc8AnJ1FY9uk9rCnmmiWVGwYsLUA@mail.gmail.com>
Date:   Tue, 25 Jul 2023 11:41:50 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Feng Liu <feliu@...dia.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Bodong Wang <bodong@...dia.com>,
        Parav Pandit <parav@...dia.com>, Jiri Pirko <jiri@...dia.com>
Subject: Re: [PATCH v1] virtio-pci: Fix legacy device flag setting error in probe

On Mon, Jul 24, 2023 at 9:14 PM Feng Liu <feliu@...dia.com> wrote:
>
>
>
> On 2023-07-20 p.m.1:14, Michael S. Tsirkin wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Thu, Jul 20, 2023 at 10:27:04AM +0800, Jason Wang wrote:
> >> On Wed, Jul 19, 2023 at 11:46 PM Feng Liu <feliu@...dia.com> wrote:
> >>>
> >>> The 'is_legacy' flag is used to differentiate between legacy vs modern
> >>> device. Currently, it is based on the value of vp_dev->ldev.ioaddr.
> >>> However, due to the shared memory of the union between struct
> >>> virtio_pci_legacy_device and struct virtio_pci_modern_device, when
> >>> virtio_pci_modern_probe modifies the content of struct
> >>> virtio_pci_modern_device, it affects the content of struct
> >>> virtio_pci_legacy_device, and ldev.ioaddr is no longer zero, causing
> >>> the 'is_legacy' flag to be set as true. To resolve issue, when legacy
> >>> device is probed, mark 'is_legacy' as true, when modern device is
> >>> probed, keep 'is_legacy' as false.
> >>>
> >>> Fixes: 4f0fc22534e3 ("virtio_pci: Optimize virtio_pci_device structure size")
> >>> Signed-off-by: Feng Liu <feliu@...dia.com>
> >>> Reviewed-by: Parav Pandit <parav@...dia.com>
> >>> Reviewed-by: Jiri Pirko <jiri@...dia.com>
> >>> ---
> >>>   drivers/virtio/virtio_pci_common.c | 2 --
> >>>   drivers/virtio/virtio_pci_legacy.c | 1 +
> >>>   2 files changed, 1 insertion(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> >>> index a6c86f916dbd..c2524a7207cf 100644
> >>> --- a/drivers/virtio/virtio_pci_common.c
> >>> +++ b/drivers/virtio/virtio_pci_common.c
> >>> @@ -557,8 +557,6 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
> >>>
> >>>          pci_set_master(pci_dev);
> >>>
> >>> -       vp_dev->is_legacy = vp_dev->ldev.ioaddr ? true : false;
> >>> -
> >>>          rc = register_virtio_device(&vp_dev->vdev);
> >>>          reg_dev = vp_dev;
> >>>          if (rc)
> >>> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> >>> index 2257f1b3d8ae..d9cbb02b35a1 100644
> >>> --- a/drivers/virtio/virtio_pci_legacy.c
> >>> +++ b/drivers/virtio/virtio_pci_legacy.c
> >>> @@ -223,6 +223,7 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
> >>>          vp_dev->config_vector = vp_config_vector;
> >>>          vp_dev->setup_vq = setup_vq;
> >>>          vp_dev->del_vq = del_vq;
> >>> +       vp_dev->is_legacy = true;
> >>
> >> This seems break force_legacy for modern device:
> >>
> >>          if (force_legacy) {
> >>                  rc = virtio_pci_legacy_probe(vp_dev);
> >>                  /* Also try modern mode if we can't map BAR0 (no IO space). */
> >>                  if (rc == -ENODEV || rc == -ENOMEM)
> >>                          rc = virtio_pci_modern_probe(vp_dev);
> >>
> >> Thanks
> >
> > don't see the breakage here - can you explain a bit more?
> >
> Hi, Jason
>
> I also think there is no breakage herea and gave an explanation in
> another email, please have a see.

I think I've made a mistake, the patch should be fine.

>
> So are there any comments about this bug fix patch? Can this patch pass
> the review?

Yes.

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks

>
> Thanks
> Feng
>
> >>>
> >>>          return 0;
> >>>   }
> >>> --
> >>> 2.37.1 (Apple Git-137.1)
> >>>
> >
>