Re: [Xen-devel] [PATCH v4 04/17] xen/arm: ITS: Add helper functions to manage its_devices

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Vijay,

On 10/07/2015 09:42, vijay.kilari@xxxxxxxxx wrote:
> ---
>   xen/arch/arm/gic-v3-its.c     |   49 +++++++++++++++++++++++++++++++++++++++++
>   xen/include/asm-arm/gic-its.h |   13 +++++++++++
>   2 files changed, 62 insertions(+)
>
> diff --git a/xen/arch/arm/gic-v3-its.c b/xen/arch/arm/gic-v3-its.c
> index 60ab646..b421a6f 100644
> --- a/xen/arch/arm/gic-v3-its.c
> +++ b/xen/arch/arm/gic-v3-its.c
> @@ -90,6 +90,7 @@ struct its_node {
>   static LIST_HEAD(its_nodes);
>   static DEFINE_SPINLOCK(its_lock);
>   static struct rdist_prop  *gic_rdists;
> +static struct rb_root rb_its_dev;
>
>   #define gic_data_rdist()    (per_cpu(rdist, smp_processor_id()))
>
> @@ -101,6 +102,53 @@ void dump_cmd(its_cmd_block *cmd)
>   }
>   #endif
>
> +/* RB-tree helpers for its_device */
> +struct its_device *its_find_device(u32 devid)
> +{
> +    struct rb_node *node = rb_its_dev.rb_node;
> +
> +    while ( node )
> +    {
> +        struct its_device *dev;
> +
> +        dev = container_of(node, struct its_device, node);
> +        if ( devid < dev->device_id )
> +            node = node->rb_left;
> +        else if ( devid > dev->device_id )
> +            node = node->rb_right;
> +        else
> +            return dev;
> +    }
> +
> +    return NULL;
> +}
> +
> +int its_insert_device(struct its_device *dev)
> +{
> +    struct rb_node **new, *parent;
> +
> +    new = &rb_its_dev.rb_node;
> +    parent = NULL;
> +    while ( *new )
> +    {
> +        struct its_device *this;
> +
> +        this  = container_of(*new, struct its_device, node);
> +        parent = *new;
> +        if ( dev->device_id < this->device_id )
> +            new = &((*new)->rb_left);
> +        else if ( dev->device_id > this->device_id )
> +            new = &((*new)->rb_right);
> +        else
> +            return -EEXIST;
> +    }
> +
> +    rb_link_node(&dev->node, parent, new);
> +    rb_insert_color(&dev->node, &rb_its_dev);
> +
> +    return 0;
> +}
> +
>   #define ITS_CMD_QUEUE_SZ            SZ_64K
>   #define ITS_CMD_QUEUE_NR_ENTRIES    (ITS_CMD_QUEUE_SZ / sizeof(its_cmd_block))
>
> @@ -811,6 +859,7 @@ static int its_probe(struct dt_device_node *node)
>       list_add(&its->entry, &its_nodes);
>       spin_unlock(&its_lock);
>
> +    rb_its_dev = RB_ROOT;
NIT: missing newline here.

A general question, how do you ensure any concurrent insert to the 
RB-tree? Is it taken care by the ITS lock and the caller?
I would be ok to defer the locking for when the PCI passthrough is 
supported as all the ITS device are added when Xen is booted.
A TODO would be worth to add. With the TODO and the answer to my questions:

Reviewed-by: Julien Grall <julien.grall@xxxxxxxxxx>

Regards,

--
Julien Grall

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