Re: [PATCH 1/1] xen:vtd: missing RMRR mapping while share EPT

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

On 2014/7/24 18:11, Jan Beulich wrote:
>>>> On 24.07.14 at 11:56, <tiejun.chen@intel.com> wrote:
>> On 2014/7/24 17:41, Jan Beulich wrote:
>>>>>> On 24.07.14 at 10:28, <tiejun.chen@intel.com> wrote:
>>>> On 2014/7/24 15:45, Jan Beulich wrote:
>>>>>>>> On 24.07.14 at 09:00, <tiejun.chen@intel.com> wrote:
>>>>>> On 2014/7/24 14:14, Jan Beulich wrote:
>>>>>>>>>> On 24.07.14 at 03:23, <tiejun.chen@intel.com> wrote:
>>>>>>>> @@ -1867,7 +1869,21 @@ static int rmrr_identity_mapping(struct domain *d,
>>>>>>>>
>>>>>>>>           while ( base_pfn < end_pfn )
>>>>>>>>           {
>>>>>>>> -        if ( intel_iommu_map_page(d, base_pfn, base_pfn,
>>>>>>>> +        if ( iommu_use_hap_pt(d) )
>>>>>>>
>>>>>>> Don't you, btw, need to extend this condition by
>>>>>>> && (!iommu_passthrough || !is_hardware_domain(d))?
>>>>>>
>>>>>> Why do we need these checks here?
>>>>>
>>>>> At least for documentation purposes: It would be wrong to try to
>>>>> establish these mappings. I reckon iommu_use_hap_pt() implies the
>>>>> combined other condition, so an ASSERT() would presumably be fine
>>>>> as well (and get even closer to the intended documentation purpose).
>>>>>
>>>>
>>>> I think if() should be reasonable here. Because
>>>>
>>>> intel_iommu_map_page()
>>>> {
>>>> 	...
>>>>        /* do nothing if dom0 and iommu supports pass thru */
>>>>        if ( iommu_passthrough && is_hardware_domain(d) )
>>>>            return 0;
>>>>
>>>> We just do nothing to return simply. But if ASSERT will cause abort.
>>>
>>> Then tell me the scenario where iommu_use_hap_pt(d) is true and
>>> both iommu_passthrough and is_hardware_domain(d) are true too.
>>
>> Then HVM?
>
> If we will ever see a HVM Dom0 it'll clearly also require
> !iommu_passthrough, just like PVH does - this mode is solely for PV.
>
>> Anyway I did a test like this,
>>
>> 	if (iommu_use_hap_pt(d))
>> 	{
>> 		ASSERT (iommu_passthrough && is_hardware_domain(d));
>>
>> Then Xen really reboot.
>
> Of course, because you inverted the condition. You want
>
> 	ASSERT(!iommu_passthrough || !is_hardware_domain(d));

You're right. Sorry I'm misunderstanding this point.

Tiejun

>
> i.e. what I had previously suggested to add with && to the original
> condition.
>
> Jan
>
>