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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.11.14 at 10:51, <tiejun.chen@xxxxxxxxx> wrote:
> On 2014/11/3 17:00, Jan Beulich wrote:
>>>>> On 03.11.14 at 07:20, <tiejun.chen@xxxxxxxxx> 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).

Jan


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