Re: [virtio] [PATCH] virtio-ccw: add adapter interrupt support

[Rusty Russell <rusty@au1.ibm.com>]

Cornelia Huck <cornelia.huck@de.ibm.com> writes:
> Specify a new channel command to set up two-stage indicators as needed
> for adapter interrupts and describe how adapter interrupts are used
> for notifications.

Since this presumably isn't in the current implementation, should there
be a legacy section talking about what happens if it's not supported?
Or is that implied and I missed it?

Nice to see that CCW is getting some benefit from the pain of v1.0 :)

> VIRTIO-43
>
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  virtio-v1.0-wd01-part1-specification.txt |  100 ++++++++++++++++++++++++++++--
>  1 file changed, 96 insertions(+), 4 deletions(-)
>
> diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
> index 3ba7f52..ae646db 100644
> --- a/virtio-v1.0-wd01-part1-specification.txt
> +++ b/virtio-v1.0-wd01-part1-specification.txt
> @@ -1545,6 +1545,7 @@ virtio:
>  #define CCW_CMD_VDEV_RESET 0x33
>  #define CCW_CMD_SET_IND 0x43
>  #define CCW_CMD_SET_CONF_IND 0x53
> +#define CCW_CMD_SET_IND_ADAPTER 0x73
>  #define CCW_CMD_READ_FEAT 0x12
>  #define CCW_CMD_WRITE_FEAT 0x11
>  #define CCW_CMD_READ_CONF 0x22
> @@ -1724,15 +1725,74 @@ In both cases, the complete configuration space is transmitted.
>  2.3.3.2.6. Setting Up Indicators
>  --------------------------------
>  
> +In order to set up the indicator bits for host->guest notification,
> +the driver uses different channel commands depending on whether it
> +wishes to use traditional I/O interrupts tied to a subchannel or
> +adapter I/O interrupts. For any given device, the two mechanisms
> +are mutually exclusive.
> +
> +For the configuration change indicators, the same mechanism is used
> +in both cases.
> +
> +2.3.3.2.6.1. Setting Up Classic Queue Indicators
> +------------------------------------------------
> +
> +Indicators for notification via classic I/O interrupts are contained
> +in a 64 bit value per virtio-ccw proxy device.
> +
>  To communicate the location of the indicator bits for host->guest
>  notification, the guest uses the CCW_CMD_SET_IND command,
>  pointing to a location containing the guest address of the
>  indicators in a 64 bit value.
>  
> -For the indicator bits used in the configuration change
> -host->guest notification, the CCW_CMD_SET_CONF_IND command is
> -used analogously.
> +If the driver has already set up two-staged queue indicators via the
> +CCW_CMD_SET_IND_ADAPTER command, the device MUST post a unit check
> +with command reject to any subsequent CCW_CMD_SET_IND command.
> +
> +2.3.3.2.6.2. Setting Up Configuration Change Indicators
> +-------------------------------------------------------
> +
> +Indicators for configuration change host->guest notification are
> +contained in a 64 bit value per virtio-ccw proxy device.
> +
> +To communicate the location of the indicator bits used in the
> +configuration change host->guest notification, the driver issues the
> +CCW_CMD_SET_CONF_IND command, pointing to a location containing the
> +guest address of the indicators in a 64 bit value.
> +
> +2.3.3.2.6.3. Setting Up Two-Stage Queue Indicators
> +--------------------------------------------------
> +
> +Indicators for notification via adapter I/O interrupts consist of
> +two stages:
> +- a summary indicator byte covering the virtqueues for one or more
> +  virtio-ccw proxy devices
> +- a set of contigous indicator bits for the virtqueues for a
> +  virtio-ccw proxy device
> +
> +To communicate the location of the summary and queue indicator bits,
> +the driver uses the CCW_CMD_SET_IND_ADAPTER command with the following
> +payload:
> +
> +struct virtio_thinint_area {
> +       __u64 summary_indicator;
> +       __u64 indicator;
> +       __u64 bit_nr;
> +       __u8 isc;
> +};

Hmm... you __attribute__((packed)) the other structures; I assume
that's wanted here too?

Cheers,
Rusty.