Re: [PATCH RFC 05/12] remoteproc: always report VIRTIO_F_VERSION_1 feature
From: Mathieu Poirier <mathieu.poirier@linaro.org>
Date: 2026-09-21 15:47:58
Also in:
imx, linux-devicetree, linux-iommu, linux-remoteproc, lkml, virtualization
On Wed, Sep 16, 2026 at 11:10:50PM +0200, Francesco Valla wrote:
quoted hunk ↗ jump to hunk
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, as some drivers depend on it. Signed-off-by: Francesco Valla <redacted> --- drivers/remoteproc/remoteproc_virtio.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c index 74e0da970f1d..cfd66d9d1c9e 100644 --- a/drivers/remoteproc/remoteproc_virtio.c +++ b/drivers/remoteproc/remoteproc_virtio.c@@ -249,7 +249,7 @@ static u64 rproc_virtio_get_features(struct virtio_device *vdev) rsc = (void *)rvdev->rproc->table_ptr + rvdev->rsc_offset; - return rsc->dfeatures; + return rsc->dfeatures | (1ULL << VIRTIO_F_VERSION_1);
I understand this.
quoted hunk ↗ jump to hunk
} static void rproc_transport_features(struct virtio_device *vdev)@@ -275,14 +275,16 @@ 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 VIRTIO_F_VERSION_1 */ + if (WARN_ON_ONCE((u32)vdev->features != + (vdev->features & ~(1ULL << VIRTIO_F_VERSION_1)))) + return -1;
And this.
/* * Remember the finalized features of our vdev, and provide it * to the remote processor once it is powered on. */ - rsc->gfeatures = vdev->features; + rsc->gfeatures = vdev->features & ~(1ULL << VIRTIO_F_VERSION_1);
But I'm having trouble with this one. First bit 32 of vdev->features gets cleared and then bit 0 to 31 are assigned to rsc->gfeatures. Why bother with clearing bit 32?
return 0; } -- 2.55.0