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

[Francesco Valla]

Hi Mathieu,

10 Nov 2026 16:46:09 Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>:

> 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.

Take your time, I'm in no rush to have this merged.

> That said, I applied the first 2 patches so no need to include them in the next
> revision.

Ok!

>
> Thanks,
> Mathieu
>

Thank you!

Regards,
Francesco

> 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@xxxxxxxx>
>> ---
>> 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
>>