Re: [RFC 4/11] virtio-pci: define layout for virtio vendor-specific capabilities.

[Sasha Levin <levinsasha928@gmail.com>]

On Thu, 2011-12-08 at 21:04 +1030, Rusty Russell wrote:
> Based on patch by Michael S. Tsirkin <mst@redhat.com>, but I found it
> hard to follow so changed to use structures which are more
> self-documenting.
> 
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> ---
>  include/linux/virtio_pci.h |   41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/include/linux/virtio_pci.h b/include/linux/virtio_pci.h
> --- a/include/linux/virtio_pci.h
> +++ b/include/linux/virtio_pci.h
> @@ -92,4 +92,45 @@
>  /* The alignment to use between consumer and producer parts of vring.
>   * x86 pagesize again. */
>  #define VIRTIO_PCI_VRING_ALIGN		4096
> +
> +/* IDs for different capabilities.  Must all exist. */
> +/* FIXME: Do we win from separating ISR, NOTIFY and COMMON? */
> +/* Common configuration */
> +#define VIRTIO_PCI_CAP_COMMON_CFG	1
> +/* Notifications */
> +#define VIRTIO_PCI_CAP_NOTIFY_CFG	2
> +/* ISR access */
> +#define VIRTIO_PCI_CAP_ISR_CFG		3
> +/* Device specific confiuration */
> +#define VIRTIO_PCI_CAP_DEVICE_CFG	4
> +
> +/* This is the PCI capability header: */
> +struct virtio_pci_cap {
> +	u8 cap_vndr;	/* Generic PCI field: PCI_CAP_ID_VNDR */
> +	u8 cap_next;	/* Generic PCI field: next ptr. */

There should be a cap_len field here, which is mandatory for
PCI_CAP_ID_VNDR capabilities.

> +	u8 cfg_type;	/* One of the VIRTIO_PCI_CAP_*_CFG. */
> +/* FIXME: Should we use a bir, instead of raw bar number? */
> +	u8 bar;		/* Where to find it. */
> +	__le32 offset;	/* Offset within bar. */
> +	__le32 length;	/* Length. */
> +};
> +
> +/* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
> +struct virtio_pci_common_cfg {
> +	/* About the whole device. */
> +	__le32 device_feature_select;	/* read-write */
> +	__le32 device_feature;		/* read-only */
> +	__le32 guest_feature_select;	/* read-write */
> +	__le32 guest_feature;		/* read-only */
> +	__le16 msix_config;		/* read-write */
> +	__u8 device_status;		/* read-write */
> +	__u8 unused;
> +
> +	/* About a specific virtqueue. */
> +	__le16 queue_select;	/* read-write */
> +	__le16 queue_align;	/* read-write, power of 2. */
> +	__le16 queue_size;	/* read-write, power of 2. */
> +	__le16 queue_msix_vector;/* read-write */
> +	__le64 queue_address;	/* read-write: 0xFFFFFFFFFFFFFFFF == DNE. */

This is now a 64bit address, but we can't do an atomic iowrite64(). We
should make it clear to the device when it should initialize the vq.

-- 

Sasha.