Re: [PATCH V1 18/29] xen/arm: Don't map disabled device in DOM0

[Julien Grall <julien.grall@linaro.org>]

On 09/09/2013 12:40 PM, Ian Campbell wrote:
> On Wed, 2013-08-28 at 15:47 +0100, Julien Grall wrote:
>> Linux should cope with 'status = "disabled"' in the Device Tree.
>
> This is devices which were disabled in the DT passed to Xen, rather than
> ones which we have disabled ourselves (e.g. the previous patch)?

Yes.


>> This solution can be used later to pass-through device to a specific guest.
>
> How? I thought disabled meant "not present/wired-up on this variant of
> the platform"? A user cannot be expected to edit the host DTB to enable
> passthrough. We might want a dtb_hide cmdline option, or to do it
> dynamically like pciback is capable of.

Disabled also means "the device is not presently operational, but it 
might become operational in the future".

> Or maybe I'm wrong above and this is indeed devices we have disabled
> ourselves?

I'm not sure it's usefull. But I don't see any reason to map disabled 
device in dom0.


>>
>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
>>
>> ---
>>      Changes in v2:
>>          - Add a comment
>> ---
>>   xen/arch/arm/domain_build.c |    6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index d56bc70a..11f247b 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -416,9 +416,13 @@ static int handle_node(struct domain *d, struct kernel_info *kinfo,
>>        *  - Device used by Xen: Obviously dom0 can't use them
>>        *  - Memory: the guest will see a different view of memory. It will
>>        *  be allocated later.
>> +     *  - Disabled device: Linux is able to cope with status="disabled"
>> +     *  property. Therefore these device doesn't need to be mapped. This
>> +     *  solution can be use later for pass through.
>>        */
>>       if ( dt_device_used_by(np) != DOMID_XEN &&
>> -         !dt_device_type_is_equal(np, "memory") )
>> +         !dt_device_type_is_equal(np, "memory") &&
>> +         dt_device_is_available(np) )
>>       {
>>           res = map_device(d, np);
>>
>
>


-- 
Julien Grall