linux-kernel - Re: [PATCH v8 06/50] virtio_ccw: add support for 64 bit features.

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Message-ID: <20141202121432.6ceb79b5@oc7435384737.ibm.com>
Date:	Tue, 2 Dec 2014 12:14:32 +0100
From:	Thomas Huth <thuth@...ux.vnet.ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	cornelia.huck@...ibm.com, rusty@....ibm.com, nab@...ux-iscsi.org,
	pbonzini@...hat.com, dahi@...ux.vnet.ibm.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux390@...ibm.com, Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-s390@...r.kernel.org
Subject: Re: [PATCH v8 06/50] virtio_ccw: add support for 64 bit features.

On Mon, 1 Dec 2014 18:03:17 +0200
"Michael S. Tsirkin" <mst@...hat.com> wrote:

> Negotiate full 64 bit features.
> Change u32 to u64, make sure to use 1ULL everywhere.
> 
> Note: devices guarantee that VERSION_1 is clear unless
> revision 1 is negotiated.
> 
> Note: We don't need to re-setup the ccw, but we do it
> for clarity.
> 
> Based on patches by Rusty, Thomas Huth and Cornelia.
> 
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> Signed-off-by: Cornelia Huck <cornelia.huck@...ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> Reviewed-by: David Hildebrand <dahi@...ux.vnet.ibm.com>
> ---
>  drivers/s390/kvm/virtio_ccw.c | 30 +++++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> index 244d611..65d0c80 100644
> --- a/drivers/s390/kvm/virtio_ccw.c
> +++ b/drivers/s390/kvm/virtio_ccw.c
> @@ -664,7 +664,8 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
>  {
>  	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
>  	struct virtio_feature_desc *features;
> -	int ret, rc;
> +	int ret;
> +	u64 rc;
>  	struct ccw1 *ccw;
> 
>  	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
> @@ -677,7 +678,6 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
>  		goto out_free;
>  	}
>  	/* Read the feature bits from the host. */
> -	/* TODO: Features > 32 bits */
>  	features->index = 0;
>  	ccw->cmd_code = CCW_CMD_READ_FEAT;
>  	ccw->flags = 0;
> @@ -691,6 +691,16 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
> 
>  	rc = le32_to_cpu(features->features);
> 
> +	/* Read second half of the feature bits from the host. */
> +	features->index = 1;
> +	ccw->cmd_code = CCW_CMD_READ_FEAT;
> +	ccw->flags = 0;
> +	ccw->count = sizeof(*features);
> +	ccw->cda = (__u32)(unsigned long)features;
> +	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_FEAT);
> +	if (ret == 0)
> +		rc |= (u64)le32_to_cpu(features->features) << 32;
> +
>  out_free:
>  	kfree(features);
>  	kfree(ccw);
> @@ -714,12 +724,18 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
>  	/* Give virtio_ring a chance to accept features. */
>  	vring_transport_features(vdev);
> 
> -	/* Make sure we don't have any features > 32 bits! */
> -	BUG_ON((u32)vdev->features != vdev->features);
> -
>  	features->index = 0;
> -	features->features = cpu_to_le32(vdev->features);
> -	/* Write the feature bits to the host. */
> +	features->features = cpu_to_le32((u32)vdev->features);
> +	/* Write the first half of the feature bits to the host. */
> +	ccw->cmd_code = CCW_CMD_WRITE_FEAT;
> +	ccw->flags = 0;
> +	ccw->count = sizeof(*features);
> +	ccw->cda = (__u32)(unsigned long)features;
> +	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
> +
> +	features->index = 1;
> +	features->features = cpu_to_le32(vdev->features >> 32);
> +	/* Write the second half of the feature bits to the host. */
>  	ccw->cmd_code = CCW_CMD_WRITE_FEAT;
>  	ccw->flags = 0;
>  	ccw->count = sizeof(*features);

Looks fine!

Reviewed-by: Thomas Huth <thuth@...ux.vnet.ibm.com>

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