On Sun, 8 Oct 2023 06:42:37 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> On Sun, Oct 08, 2023 at 05:38:41PM +0800, Xuan Zhuo wrote:
> > Now, the function vp_modern_map_capability() takes the size parameter,
> > which corresponds to the size of virtio_pci_common_cfg. As a result,
> > this indicates the size of memory area to map.
> >
> > However, if the _F_RING_RESET is negotiated, the extra items will be
> > used. Therefore, we need to use the size of virtio_pci_modern_common_cfg
> > to map more space.
> >
> > Meanwhile, this patch removes the feature(_F_RING_ERSET and
>
> typo
>
> > _F_NOTIFICATION_DATA) when the common cfg size does not match
> > the corresponding feature.
> >
> > Fixes: 0b50cece0b78 ("virtio_pci: introduce helper to get/set queue reset")
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/virtio/virtio_pci_modern.c | 20 +++++++++++++++++++-
> > drivers/virtio/virtio_pci_modern_dev.c | 4 ++--
> > include/linux/virtio_pci_modern.h | 1 +
> > 3 files changed, 22 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index d6bb68ba84e5..c0b9d2363ddb 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -22,8 +22,26 @@
> > static u64 vp_get_features(struct virtio_device *vdev)
> > {
> > struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> > + u64 features = vp_modern_get_features(&vp_dev->mdev);
> > +
> > +#define check_feature(feature, field) \
> > + do { \
> > + if (features & BIT_ULL(feature)) { \
> > + u32 offset = offsetofend(struct virtio_pci_modern_common_cfg, field); \
> > + if (unlikely(vp_dev->mdev.common_len < offset)) \
> > + features &= ~BIT_ULL(feature); \
> > + } \
> > + } while (0)
> > +
> > + /* For buggy devices, if the common len does not match the feature, we
> > + * remove the feature.
>
> I don't like doing this in vp_get_features. userspace won't be able
> to see the actual device features at all.
> Also, we should print an info message at least.
>
> I am still debating with myself whether clearing feature bits
> or just failing finalize_features (and thus, probe) is best.
For me, I think failing probe is best.
Then the developer of the device can find that firstly.
And I think we should print an info message when we detect
this error.
If we clear the feature bits, the developer of the device may
ignore this error.
>
>
> > + */
> > + check_feature(VIRTIO_F_NOTIFICATION_DATA, queue_notify_data);
> > + check_feature(VIRTIO_F_RING_RESET, queue_reset);
> > +
> > +#undef check_feature
>
> this macro's too scary. just pass offset and feature bit as
> parameters to an inline function.
I should pass the features as a parameter.
Thanks.
>
> >
> > - return vp_modern_get_features(&vp_dev->mdev);
> > + return features;
> > }
> >
> > static void vp_transport_features(struct virtio_device *vdev, u64 features)
> > diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> > index aad7d9296e77..33f319da1558 100644
> > --- a/drivers/virtio/virtio_pci_modern_dev.c
> > +++ b/drivers/virtio/virtio_pci_modern_dev.c
> > @@ -291,8 +291,8 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
> > err = -EINVAL;
> > mdev->common = vp_modern_map_capability(mdev, common,
> > sizeof(struct virtio_pci_common_cfg), 4,
> > - 0, sizeof(struct virtio_pci_common_cfg),
> > - NULL, NULL);
> > + 0, sizeof(struct virtio_pci_modern_common_cfg),
> > + &mdev->common_len, NULL);
> > if (!mdev->common)
> > goto err_map_common;
> > mdev->isr = vp_modern_map_capability(mdev, isr, sizeof(u8), 1,
> > diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
> > index 067ac1d789bc..edf62bae0474 100644
> > --- a/include/linux/virtio_pci_modern.h
> > +++ b/include/linux/virtio_pci_modern.h
> > @@ -28,6 +28,7 @@ struct virtio_pci_modern_device {
> > /* So we can sanity-check accesses. */
> > size_t notify_len;
> > size_t device_len;
> > + size_t common_len;
> >
> > /* Capability for when we need to map notifications per-vq. */
> > int notify_map_cap;
> > --
> > 2.32.0.3.g01195cf9f
>
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