Re: ARM Xen Bug #45: Is there a solution?

[Julien Grall <julien.grall@arm.com>]

Hello Dirk,

On 27/05/16 13:34, Dirk Behme wrote:
> On 26.05.2016 11:00, Julien Grall wrote:
>> On 25/05/2016 16:10, Dirk Behme wrote:
>>> On 24.05.2016 22:05, Julien Grall wrote:
>>>> On 24/05/2016 14:39, Dirk Behme wrote:
>>>>> On 23.05.2016 22:15, Julien Grall wrote:
>> All the devices (UART included) used by Xen will return DOMID_XEN when
>> dt_device_used_by is called to the node.
>>
>> You could use it to collect the clocks of all those devices and gather
>> the value in a single property to be created in the hypervisor node.
>
>
> Anything like below (untested) [1]?

Yes.

> I'm unhappy about the global variables and the max clocks, though.

How about moving those variables in the structure kernel_info?

>
> Best regards
>
> Dirk
>
> [1]
>
> ---
>   xen/arch/arm/domain_build.c |   24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
>
> Index: xen.git/xen/arch/arm/domain_build.c
> ===================================================================
> --- xen.git.orig/xen/arch/arm/domain_build.c
> +++ xen.git/xen/arch/arm/domain_build.c
> @@ -42,6 +42,10 @@ static void __init parse_dom0_mem(const
>   }
>   custom_param("dom0_mem", parse_dom0_mem);
>
> +#define MAX_DT_CLOCKS 256
> +static unsigned char dt_clocks[MAX_DT_CLOCKS];
> +static unsigned int clk_cnt;
> +
>   //#define DEBUG_DT
>
>   #ifdef DEBUG_DT
> @@ -657,6 +661,10 @@ static int make_hypervisor_node(const st
>       if ( res )
>           return res;
>
> +    res = fdt_property(fdt, "clocks", dt_clocks, clk_cnt);
> +    if ( res )
> +        return res;
> +
>       res = fdt_end_node(fdt);
>
>       return res;
> @@ -1213,9 +1221,11 @@ static int handle_node(struct domain *d,
>           { /* sentinel */ },
>       };
>       struct dt_device_node *child;
> +    unsigned int len;
>       int res;
>       const char *name;
>       const char *path;
> +    const char *clocks;
>
>       path = dt_node_full_name(node);
>
> @@ -1246,6 +1256,20 @@ static int handle_node(struct domain *d,
>       if ( dt_device_used_by(node) == DOMID_XEN )
>       {
>           DPRINT("  Skip it (used by Xen)\n");
> +
> +        /*
> +         * Remember the clock used by the skipped node
> +         * We add it later to the hypervisor node to make the
> +         * Linux kernel aware of its usage
> +         */
> +        clocks = dt_get_property(node, "clocks", &len);
> +        if ( clk_cnt + len >= MAX_DT_CLOCKS ) {
> +            printk("Failed to remember the clock node of %s\n", path);
> +            printk("Use the Linux kernel command 'clk_ignore_unused'\n");
> +            return 0;
> +        }
> +        memcpy(&dt_clocks[clk_cnt], clocks, len);
> +        clk_cnt += len;
>           return 0;
>       }
>

-- 
Julien Grall

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