Re: [PATCH RFC v2 04/11] remoteproc: report VIRTIO_F_VERSION_1 for non-rproc-specific vdevs

[Mathieu Poirier <mathieu.poirier@linaro.org>]

Hi,

I started reviewing this set, making it to this patch.  I will continue tomorrow
but due to the KVM forum later this week, I may not finish before next week.
That said, I applied the first 2 patches so no need to include them in the next
revision.

Thanks,
Mathieu

On Mon, Nov 02, 2026 at 12:26:41AM +0100, Francesco Valla wrote:
> There is currently no way to report the VIRTIO_F_VERSION_1 using the
> resource table alone, as the per-vdev feature array is limited to 32
> bits.
> 
> Considering that the VIRTIO 1.0 specification is now ~10 years old,
> always report the VIRTIO_F_VERSION_1 feature for virtio devices that
> are not specific for remoteproc usage. These latter, which as of today
> are rpmsg and rproc-serial, are excluded to avoid impacting the existing
> usecases, since VIRTIO_F_VERSION_1 changes the semantics of the
> communication (e.g., the configuration space is assumed to be
> little-endian rather than follow the device's endianness).
> 
> While at it, replace BUG_ON() with WARN_ON() and return an appropriate
> error in case of features that would overflow the 32 bits limit.
> 
> Signed-off-by: Francesco Valla <francesco@valla.it>
> ---
>  drivers/remoteproc/remoteproc_virtio.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
> index c56d3330adfe..f1b362158a9c 100644
> --- a/drivers/remoteproc/remoteproc_virtio.c
> +++ b/drivers/remoteproc/remoteproc_virtio.c
> @@ -16,6 +16,7 @@
>  #include <linux/of_reserved_mem.h>
>  #include <linux/platform_device.h>
>  #include <linux/remoteproc.h>
> +#include <linux/rsc_table.h>
>  #include <linux/virtio.h>
>  #include <linux/virtio_config.h>
>  #include <linux/virtio_ids.h>
> @@ -27,6 +28,11 @@
>  
>  #include "remoteproc_internal.h"
>  
> +static bool rproc_virtio_rsc_vdev_rproc_specific(struct fw_rsc_vdev *rsc)
> +{
> +	return (rsc->id == VIRTIO_ID_RPMSG || rsc->id == VIRTIO_ID_RPROC_SERIAL);
> +}
> +
>  static int copy_dma_range_map(struct device *to, struct device *from)
>  {
>  	const struct bus_dma_region *map = from->dma_range_map, *new_map, *r;
> @@ -268,8 +274,17 @@ static void rproc_virtio_synchronize_cbs(struct virtio_device *vdev)
>  static u64 rproc_virtio_get_features(struct virtio_device *vdev)
>  {
>  	struct fw_rsc_vdev *rsc = vdev_to_rsc(vdev);
> +	u64 features = (u64)rsc->dfeatures;
>  
> -	return rsc->dfeatures;
> +	/*
> +	 * All non-remoteproc-specific virtio devices are assumed to be
> +	 * compliant with virtio specifications 1.x; there is no other method
> +	 * to transmit this capability from the remote processor to the host.
> +	 */
> +	if (!rproc_virtio_rsc_vdev_rproc_specific(rsc))
> +		features |= (1ULL << VIRTIO_F_VERSION_1);
> +
> +	return features;
>  }
>  
>  static void rproc_transport_features(struct virtio_device *vdev)
> @@ -285,6 +300,7 @@ static void rproc_transport_features(struct virtio_device *vdev)
>  static int rproc_virtio_finalize_features(struct virtio_device *vdev)
>  {
>  	struct fw_rsc_vdev *rsc = vdev_to_rsc(vdev);
> +	u64 features;
>  
>  	/* Give virtio_ring a chance to accept features */
>  	vring_transport_features(vdev);
> @@ -292,8 +308,14 @@ static int rproc_virtio_finalize_features(struct virtio_device *vdev)
>  	/* Give virtio_rproc a chance to accept features. */
>  	rproc_transport_features(vdev);
>  
> -	/* Make sure we don't have any features > 32 bits! */
> -	BUG_ON((u32)vdev->features != vdev->features);
> +	/* Make sure we don't have any features > 32 bits except the expected ones. */
> +	features = vdev->features;
> +
> +	if (!rproc_virtio_rsc_vdev_rproc_specific(rsc))
> +		features &= ~(1ULL << VIRTIO_F_VERSION_1);
> +
> +	if (WARN_ON((u32)vdev->features != features))
> +		return -EINVAL;
>  
>  	/*
>  	 * Remember the finalized features of our vdev, and provide it
> 
> -- 
> 2.56.0
>