Re: [v7][RFC][PATCH 08/13] xen/x86/p2m: set p2m_access_n for reserved device memory mapping

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/11/3 18:03, Jan Beulich wrote:
>>>> On 03.11.14 at 10:51, <tiejun.chen@intel.com> wrote:
>> On 2014/11/3 17:00, Jan Beulich wrote:
>>>>>> On 03.11.14 at 07:20, <tiejun.chen@intel.com> wrote:
>>>> #2 the error handling
>>>>
>>>> In an error case what should I do? Currently we still create these
>>>> mapping as normal. This means these mfns will be valid so later we can't
>>>> set them again then device can't be assigned as passthrough. I think
>>>> this makes sense. Or we should just stop them from setting 1:1 mapping?
>>>
>>> You should, with very few exceptions, not ignore errors (which
>>> includes "handling" them by just logging a message. Instead, you
>>> should propagate the error back up the call chain.
>>>
>>
>> Do you mean in your patch,
>>
>> +int iommu_get_reserved_device_memory(iommu_grdm_t *func, void *ctxt)
>> +{
>> +    const struct iommu_ops *ops = iommu_get_ops();
>> +
>> +    if ( !iommu_enabled || !ops->get_reserved_device_memory )
>> +        return 0;
>> +
>> +    return ops->get_reserved_device_memory(func, ctxt);
>> +}
>> +
>>
>> I shouldn't return that directly. Then instead, we should handle all
>> error scenarios here?
>
> No. All error scenarios are already being handled here (by
> propagating the error code to the caller).

Sorry, how to propagate the error code?

Thanks
Tiejun