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

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Message-ID: <CACGkMEv1b698NcpZHxpDoNokWH0gEs07D2eYSAjsiF1efhxORw@mail.gmail.com>
Date:   Thu, 20 Jul 2023 10:27:04 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Feng Liu <feliu@...dia.com>
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        "Michael S . Tsirkin" <mst@...hat.com>,
        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 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

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