Re: [PATCH v3 1/3] xen/arm: gic: Check the size of the CPU and vCPU interface retrieved from DT

[Ian Campbell <ian.campbell@citrix.com>]

On Mon, 2015-10-05 at 15:17 +0100, Julien Grall wrote:
> @@ -641,7 +643,29 @@ static int __init gicv2_init(void)
>          panic("GICv2: Cannot find the maintenance IRQ");
>      gicv2_info.maintenance_irq = res;
>  
> -    /* TODO: Add check on distributor, cpu size */
> +    /* TODO: Add check on distributor */
> +
> +    /*
> +     * The GICv2 CPU interface should at least be 8KB. Although, most of the DT
> +     * doesn't correctly set it and use the GICv1 CPU interface size (i.e 4KB).
> +     * Warn and then fixup.
> +     */
> +    if ( csize < SZ_8K )
> +    {
> +        printk(XENLOG_WARNING "GICv2: WARNING: "
> +               "The GICC size is wrong: %#"PRIx64" expected %#x\n",
> +               csize, SZ_8K);

"is too small"?


> +        csize = SZ_8K;
> +    }
> +
> +    /*
> +     * Check if the CPU interface and virtual CPU interface have the
> +     * same size.
> +     */
> +    if ( csize != vsize )
> +        printk(XENLOG_WARNING "GICv2: WARNING: "
> +               "Sizes of GICC (%#"PRIpaddr") and GICV (%#"PRIpaddr") don't match\n",
> +               csize, vsize);

Should we also force them to be equal? Either
	csize = vsize = min(csize,vsize)
or
	vsize = csize

(probably the first)?

 
> +    /*
> +     * Only allow support of GICv2 compatible when the CPU interface
> +     * and virtual CPU interface are 8KB
> +     * XXX: Handle other size?
> +     */
> +    if ( csize != SZ_8K && vsize != SZ_8K )

I think you meant || ? Otherwise this is happy so long as one of them is
right rather than requiring both of them to be 8K.

WRT to the XXX I think I'd be happier if this was < SZ_8K for each.
Otherwise some future GIC which is compatible but has extensions to the
register space would needlessly require changes here. But I can live with
this.