linux-kernel - Re: [PATCH] virtio_mmio: generation support

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Message-ID: <87y4n3vuh6.fsf@rustcorp.com.au>
Date:	Thu, 12 Mar 2015 12:37:49 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:	virtualization@...ts.linux-foundation.org,
	Pawel Moll <pawel.moll@....com>
Subject: Re: [PATCH] virtio_mmio: generation support

"Michael S. Tsirkin" <mst@...hat.com> writes:
> virtio_mmio currently lacks generation support which
> makes multi-byte field access racy.
> Fix by getting the value at offset 0xfc for version 2
> devices. Nothing we can do for version 1, so return
> generation id 0.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>
> Pawel, you mentioned you have a working virtio 1.0
> hypervisor, can you pls confirm this works correctly?

I've applied this one, but fixed it to compile:

>  drivers/virtio/virtio_mmio.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 0375456..69b2e4d 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -237,6 +237,16 @@ static void vm_set(struct virtio_device *vdev, unsigned offset,
>  	}
>  }
>  
> +static u32 vm_generation(struct virtio_device *vdev)
> +{
> +	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> +
> +	if (vm_dev->version == 1)
> +		return 0;
> +	else
> +		return readl(vm_dev->base + VIRTIO_MMIO_CONFIG_GENERATION);
> +}
> +
>  static u8 vm_get_status(struct virtio_device *vdev)
>  {
>  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> @@ -503,6 +513,8 @@ static const char *vm_bus_name(struct virtio_device *vdev)
>  static const struct virtio_config_ops virtio_mmio_config_ops = {
>  	.get		= vm_get,
>  	.set		= vm_set,
> +	.generation	= vm_generation,
> +	.get_status	= vm_get_status,
>  	.get_status	= vm_get_status,

See the double-assingment of get_status?

Thanks,
Rusty.
PS.  Sorry, that *does* actually compile.  I wish it didn't though...
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