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

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Message-Id: <8B1FC0C7-9BAC-498D-B1F0-0138EACF75C2@arista.com>
Date:   Fri, 29 Mar 2019 15:26:46 +0000
From:   James Sewart <jamessewart@...sta.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     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

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.


Download attachment "0001-iommu-Move-iommu_group_create_direct_mappings-to-aft.patch" of type "application/octet-stream" (1252 bytes)

Download attachment "0002-iommu-vt-d-Implement-apply_resv_region-for-reserving.patch" of type "application/octet-stream" (1563 bytes)

Download attachment "0003-iommu-vt-d-Expose-ISA-direct-mapping-region-via-iomm.patch" of type "application/octet-stream" (3213 bytes)

Download attachment "0004-iommu-vt-d-Create-an-IOMMU-group-for-devices-that-re.patch" of type "application/octet-stream" (1652 bytes)

Download attachment "0005-iommu-Add-ops-entry-for-vendor-specific-default-doma.patch" of type "application/octet-stream" (2420 bytes)

Download attachment "0006-iommu-vt-d-Add-is_identity_map-ops-entry.patch" of type "application/octet-stream" (1232 bytes)

Download attachment "0007-iommu-vt-d-Enable-DMA-remapping-after-rmrr-mapped.patch" of type "application/octet-stream" (1832 bytes)

Download attachment "0008-iommu-vt-d-Allow-IOMMU_DOMAIN_DMA-to-be-allocated-by.patch" of type "application/octet-stream" (6450 bytes)

Download attachment "0009-iommu-vt-d-Remove-lazy-allocation-of-domains.patch" of type "application/octet-stream" (14028 bytes)