Re: [PATCH] virtio-mmio: add support for transport version 3

[Peter Hilber]

On Fri, Jun 05, 2026 at 04:29:21PM +0200, Peter Hilber wrote:
> Virtio MMIO transport version 3 allows device reset to complete
> asynchronously. Unlike version 2, where writing zero to Status must
> complete the reset before the write returns, version 3 requires the
> driver to poll Status until it reads back zero before considering reset
> complete.
> 
> Update virtio-mmio accordingly: accept transport version 3 and, during
> reset, wait for Status to become zero. Keep the polling loop unbounded,
> consistent with virtio-pci, since the reset callback does not return an
> error code.
> 
> Signed-off-by: Peter Hilber <peter.hilber@xxxxxxxxxxxxxxxx>
> Link: https://github.com/oasis-tcs/virtio-spec/commit/bb1dd2e1fe89b862f38f15873d835a698b196f89

Gentle ping on this patch from June 5th.

(Adding Jason's updated address, since MAINTAINERS was updated after
this was originally sent.)

Best regards,

Peter

> ---
>  drivers/virtio/virtio_mmio.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 510b7c4efdff..316f03b97356 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -55,6 +55,7 @@
>  #define pr_fmt(fmt) "virtio-mmio: " fmt
>  
>  #include <linux/acpi.h>
> +#include <linux/delay.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/highmem.h>
>  #include <linux/interrupt.h>
> @@ -114,9 +115,9 @@ static int vm_finalize_features(struct virtio_device *vdev)
>  	vring_transport_features(vdev);
>  
>  	/* Make sure there are no mixed devices */
> -	if (vm_dev->version == 2 &&
> +	if (vm_dev->version >= 2 &&
>  			!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
> -		dev_err(&vdev->dev, "New virtio-mmio devices (version 2) must provide VIRTIO_F_VERSION_1 feature!\n");
> +		dev_err(&vdev->dev, "New virtio-mmio devices (version >= 2) must provide VIRTIO_F_VERSION_1 feature!\n");
>  		return -EINVAL;
>  	}
>  
> @@ -254,6 +255,12 @@ static void vm_reset(struct virtio_device *vdev)
>  
>  	/* 0 status means a reset. */
>  	writel(0, vm_dev->base + VIRTIO_MMIO_STATUS);
> +
> +	if (vm_dev->version >= 3) {
> +		/* Wait for reset to complete. */
> +		while (vm_get_status(vdev))
> +			fsleep(1000);
> +	}
>  }
>  
>  
> @@ -600,7 +607,7 @@ static int virtio_mmio_probe(struct platform_device *pdev)
>  
>  	/* Check device version */
>  	vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);
> -	if (vm_dev->version < 1 || vm_dev->version > 2) {
> +	if (vm_dev->version < 1 || vm_dev->version > 3) {
>  		dev_err(&pdev->dev, "Version %ld not supported!\n",
>  				vm_dev->version);
>  		rc = -ENXIO;
> -- 
> 2.43.0
>