Re: [Xen-devel] [PATCH v9 23/28] ARM: vITS: handle DISCARD command

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 11/05/17 18:53, Andre Przywara wrote:
> The DISCARD command drops the connection between a DeviceID/EventID
> and an LPI/collection pair.
> We mark the respective structure entries as not allocated and make
> sure that any queued IRQs are removed.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
>  xen/arch/arm/vgic-v3-its.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
> index ef7c78f..f7a8d77 100644
> --- a/xen/arch/arm/vgic-v3-its.c
> +++ b/xen/arch/arm/vgic-v3-its.c
> @@ -723,6 +723,27 @@ out_unlock:
>      return ret;
>  }
>
> +static int its_handle_discard(struct virt_its *its, uint64_t *cmdptr)
> +{
> +    uint32_t devid = its_cmd_get_deviceid(cmdptr);
> +    uint32_t eventid = its_cmd_get_id(cmdptr);
> +    int ret;
> +
> +    spin_lock(&its->its_lock);
> +
> +    /* Remove from the radix tree and remove the host entry. */
> +    ret = its_discard_event(its, devid, eventid);
> +
> +    /* Remove from the guest's ITTE. */
> +    if ( ret || write_itte_locked(its, devid, eventid,
> +                                  UNMAPPED_COLLECTION, INVALID_LPI, NULL) )
I am not sure to fully understand this if. If ret is not NULL you 
override it and never call write_itte_locked.
Is it what you wanted? If so, then probably a bit more documentation 
would be useful to explain why writte_itte_locked is skipped.
> +        ret = -1;
> +
> +    spin_unlock(&its->its_lock);
> +
> +    return ret;
> +}
> +
>  #define ITS_CMD_BUFFER_SIZE(baser)      ((((baser) & 0xff) + 1) << 12)
>  #define ITS_CMD_OFFSET(reg)             ((reg) & GENMASK(19, 5))
>
> @@ -755,6 +776,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct 
> virt_its *its)
>          case GITS_CMD_CLEAR:
>              ret = its_handle_clear(its, command);
>              break;
> +        case GITS_CMD_DISCARD:
> +            ret = its_handle_discard(its, command);
> +            break;
>          case GITS_CMD_INT:
>              ret = its_handle_int(its, command);
>              break;
Cheers,

--
Julien Grall

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