Re: [Xen-devel] [PATCH V1 20/29] xen/arm: Create a fake cpus node in dom0 device tree

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-08-28 at 15:47 +0100, Julien Grall wrote:
> The number of cpus in dom0 can be different compare to the real number of
> physical cpus.
> 
> For the moment, Xen assumes that the cpus are identical.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/arch/arm/domain_build.c |   91 
> +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 91 insertions(+)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 4c936c1..21cd4e0 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -339,6 +339,92 @@ static int make_psci_node(void *fdt, const struct 
> dt_device_node *parent)
>      return res;
>  }
>  
> +static int make_cpus_node(const struct domain *d, void *fdt,
> +                          const struct dt_device_node *parent)
> +{
> +    int res;
> +    const struct dt_device_node *cpus = dt_find_node_by_path("/cpus");
> +    const struct dt_device_node *npcpu;
> +    unsigned int cpu;
> +    const void *compatible = NULL;
> +    u32 len;
> +    /* Placeholder for cpu@ + a 32-bit number + \0 */
> +    char buf[15];
> +
> +    DPRINT("Create cpus node\n");
> +
> +    if ( !cpus )
> +    {
> +        dprintk(XENLOG_ERR, "Missing /cpus node in the device tree?\n");
> +        return -ENOENT;
> +    }
> +
> +    /*
> +     * Get the compatible property of CPUs from the device tree.
> +     * We are assuming that all CPUs are the same

"... so we just look for the first one" would clarify what is going on
here a bit.

o/w Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> +     * TODO: Handle compatible per VCPU
> +     */
> +    for_each_child_node(cpus, npcpu)
> +    {
> +        if ( dt_device_type_is_equal(npcpu, "cpu") )
> +        {
> +            compatible = dt_get_property(npcpu, "compatible", &len);
> +            break;
> +        }
> +    }
> +
> +    if ( !compatible )
> +    {
> +        dprintk(XENLOG_ERR, "Can't find cpu in the device tree?\n");
> +        return -ENOENT;
> +    }
> +
> +    /* See Linux Documentation/devicetree/booting-without-of.txt
> +     * section III.5.b
> +     */
> +    res = fdt_begin_node(fdt, "cpus");
> +    if ( res )
> +        return res;
> +
> +    res = fdt_property_cell(fdt, "#address-cells", 1);
> +    if ( res )
> +        return res;
> +
> +    res = fdt_property_cell(fdt, "#size-cells", 0);
> +    if ( res )
> +        return res;
> +
> +    for ( cpu = 0; cpu < d->max_vcpus; cpu++ )
> +    {
> +        DPRINT("Create cpu@%u node\n", cpu);
> +
> +        snprintf(buf, sizeof(buf), "cpu@%u", cpu);
> +        res = fdt_begin_node(fdt, buf);
> +        if ( res )
> +            return res;
> +
> +        res = fdt_property(fdt, "compatible", compatible, len);
> +        if ( res )
> +            return res;
> +
> +        res = fdt_property_string(fdt, "device_type", "cpu");
> +        if ( res )
> +            return res;
> +
> +        res = fdt_property_cell(fdt, "reg", cpu);
> +        if ( res )
> +            return res;
> +
> +        res = fdt_end_node(fdt);
> +        if ( res )
> +            return res;
> +    }
> +
> +    res = fdt_end_node(fdt);
> +
> +    return res;
> +}
> +
>  /* Map the device in the domain */
>  static int map_device(struct domain *d, const struct dt_device_node *dev)
>  {
> @@ -427,6 +513,7 @@ static int handle_node(struct domain *d, struct 
> kernel_info *kinfo,
>          DT_MATCH_COMPATIBLE("xen,xen"),
>          DT_MATCH_COMPATIBLE("xen,multiboot-module"),
>          DT_MATCH_COMPATIBLE("arm,psci"),
> +        DT_MATCH_PATH("/cpus"),
>          { /* sentinel */ },
>      };
>      const struct dt_device_node *child;
> @@ -496,6 +583,10 @@ static int handle_node(struct domain *d, struct 
> kernel_info *kinfo,
>          res = make_psci_node(kinfo->fdt, np);
>          if ( res )
>              return res;
> +
> +        res = make_cpus_node(d, kinfo->fdt, np);
> +        if ( res )
> +            return res;
>      }
>  
>      res = fdt_end_node(kinfo->fdt);



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