linux-kernel - Re: [PATCH v2 3/7] iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv

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Date:   Mon, 8 Apr 2019 10:43:24 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     James Sewart <jamessewart@...sta.com>
Cc:     baolu.lu@...ux.intel.com, iommu@...ts.linux-foundation.org,
        Tom Murphy <tmurphy@...sta.com>,
        Dmitry Safonov <dima@...sta.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/7] iommu/vt-d: Expose ISA direct mapping region via
 iommu_get_resv_regions

Hi,

On 4/6/19 2:02 AM, James Sewart wrote:
> Hey Lu,
> 
> My bad, did some debugging on my end. The issue was swapping out
> find_domain for iommu_get_domain_for_dev. It seems in some situations the
> domain is not attached to the group but the device is expected to have the
> domain still stored in its archdata.
> 
> I’ve attached the final patch with find_domain unremoved which seems to
> work in my testing.

This version works for me now.

> 
> Cheers,
> James.

Best regards,
Lu Baolu

> 
> 
> 
> 
> 
>> On 4 Apr 2019, at 07:49, Lu Baolu <baolu.lu@...ux.intel.com> wrote:
>>
>> Hi James,
>>
>> I did a sanity test from my end. The test machine fails to boot. I
>> haven't seen any valuable kernel log. It results in a purple screen.
>>
>> Best regards,
>> Lu Baolu
>>
>> On 3/29/19 11:26 PM, James Sewart wrote:
>>> Hey Lu,
>>> I’ve attached a preliminary v3, if you could take a look and run some tests
>>> that would be great.
>>> Since v2 i’ve added your default domain type patches, the new device_group
>>> handler, and incorporated Jacob’s feedback.
>>>> On 28 Mar 2019, at 18:37, James Sewart <jamessewart@...sta.com> wrote:
>>>>
>>>> Hey Lu,
>>>>
>>>>> On 26 Mar 2019, at 01:24, Lu Baolu <baolu.lu@...ux.intel.com> wrote:
>>>>>
>>>>> Hi James,
>>>>>
>>>>> On 3/25/19 8:57 PM, James Sewart wrote:
>>>>>>>> Theres an issue that if we choose to alloc a new resv_region with type
>>>>>>>> IOMMU_RESV_DIRECT, we will need to refactor intel_iommu_put_resv_regions
>>>>>>>> to free this entry type which means refactoring the rmrr regions in
>>>>>>>> get_resv_regions. Should this work be in this patchset?
>>>>>>> Do you mean the rmrr regions are not allocated in get_resv_regions, but
>>>>>>> are freed in put_resv_regions? I think we should fix this in this patch
>>>>>>> set since this might impact the device passthrough if we don't do it.
>>>>>> They’re not allocated and not freed currently, only type IOMMU_RESV_MSI is
>>>>>> freed in put_resv_regions. If we allocate a new resv_region with type
>>>>>> IOMMU_RESV_DIRECT for the isa region, then it won’t be freed. If we modify
>>>>>> put_resv_regions to free type IOMMU_RESV_DIRECT, then we will try to free
>>>>>> the static RMRR regions.
>>>>>> Either the ISA region is static and not freed as with my implementation,
>>>>>> or the RMRR regions are converted to be allocated on each call to
>>>>>> get_resv_regions and freed in put_resv_regions.
>>>>>
>>>>> By the way, there's another way in my mind. Let's add a new region type
>>>>> for LPC devices, e.x. IOMMU_RESV_LPC, and then handle it in the same way
>>>>> as those MSI regions. Just FYI.
>>>>
>>>> This solution would require adding some extra code to
>>>> iommu_group_create_direct_mappings as currently only type
>>>> IOMMU_RESV_DIRECT is identity mapped, other types are only reserved.
>>>>
>>>>
>>>>>
>>>>> Best regards,
>>>>> Lu Baolu
>>>>
>>>> Cheers,
>>>> James.
>>> Cheers,
>>> James.
>