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SubjectRe: [RFC v3 00/10] KVM PCIe/MSI passthrough on ARM/ARM64 and IOVA reserved regions
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On 12/08/2016 04:36 AM, Auger Eric wrote:
> Hi,
>
> On 15/11/2016 14:09, Eric Auger wrote:
>> Following LPC discussions, we now report reserved regions through
>> iommu-group sysfs reserved_regions attribute file.
>
>
> While I am respinning this series into v4, here is a tentative summary
> of technical topics for which no consensus was reached at this point.
>
> 1) Shall we report the usable IOVA range instead of reserved IOVA
> ranges. Not discussed at/after LPC.
> x I currently report reserved regions. Alex expressed the need to
> report the full usable IOVA range instead (x86 min-max range
> minus MSI APIC window). I think this is meaningful for ARM
> too where arm-smmu might not support the full 64b range.
> x Any objection we report the usable IOVA regions instead?
>
> 2) Shall the kernel check collision with MSI window* when userspace
> calls VFIO_IOMMU_MAP_DMA?
> Joerg/Will No; Alex yes
> *for IOVA regions consumed downstream to the IOMMU: everyone says NO
>
> 3) RMRR reporting in the iommu group sysfs? Joerg: yes; Don: no
Um, I'm missing context, but the only thing I recall saying no to wrt RMRR
is that _any_ device that has an RMRR cannot be assigned to a guest.
Or, are you saying, RMRR's should be exposed in the guest os? if so, then
you have my 'no' there.

> My current series does not expose them in iommu group sysfs.
> I understand we can expose the RMRR regions in the iomm group sysfs
> without necessarily supporting RMRR requiring device assignment.
This sentence doesn't make sense to me.
Can you try re-wording it?
I can't tell what RMRR has to do w/device assignment, other than what I said above.
Exposing RMRR's in sysfs is not an issue in general.

> We can also add this support later.
>
> Thanks
>
> Eric
>
>
>>
>> Reserved regions are populated through the IOMMU get_resv_region callback
>> (former get_dm_regions), now implemented by amd-iommu, intel-iommu and
>> arm-smmu.
>>
>> The intel-iommu reports the [FEE0_0000h - FEF0_000h] MSI window as an
>> IOMMU_RESV_NOMAP reserved region.
>>
>> arm-smmu reports the MSI window (arbitrarily located at 0x8000000 and
>> 1MB large) and the PCI host bridge windows.
>>
>> The series integrates a not officially posted patch from Robin:
>> "iommu/dma: Allow MSI-only cookies".
>>
>> This series currently does not address IRQ safety assessment.
>>
>> Best Regards
>>
>> Eric
>>
>> Git: complete series available at
>> https://github.com/eauger/linux/tree/v4.9-rc5-reserved-rfc-v3
>>
>> History:
>> RFC v2 -> v3:
>> - switch to an iommu-group sysfs API
>> - use new dummy allocator provided by Robin
>> - dummy allocator initialized by vfio-iommu-type1 after enumerating
>> the reserved regions
>> - at the moment ARM MSI base address/size is left unchanged compared
>> to v2
>> - we currently report reserved regions and not usable IOVA regions as
>> requested by Alex
>>
>> RFC v1 -> v2:
>> - fix intel_add_reserved_regions
>> - add mutex lock/unlock in vfio_iommu_type1
>>
>>
>> Eric Auger (10):
>> iommu/dma: Allow MSI-only cookies
>> iommu: Rename iommu_dm_regions into iommu_resv_regions
>> iommu: Add new reserved IOMMU attributes
>> iommu: iommu_alloc_resv_region
>> iommu: Do not map reserved regions
>> iommu: iommu_get_group_resv_regions
>> iommu: Implement reserved_regions iommu-group sysfs file
>> iommu/vt-d: Implement reserved region get/put callbacks
>> iommu/arm-smmu: Implement reserved region get/put callbacks
>> vfio/type1: Get MSI cookie
>>
>> drivers/iommu/amd_iommu.c | 20 +++---
>> drivers/iommu/arm-smmu.c | 52 +++++++++++++++
>> drivers/iommu/dma-iommu.c | 116 ++++++++++++++++++++++++++-------
>> drivers/iommu/intel-iommu.c | 50 ++++++++++----
>> drivers/iommu/iommu.c | 141 ++++++++++++++++++++++++++++++++++++----
>> drivers/vfio/vfio_iommu_type1.c | 26 ++++++++
>> include/linux/dma-iommu.h | 7 ++
>> include/linux/iommu.h | 49 ++++++++++----
>> 8 files changed, 391 insertions(+), 70 deletions(-)
>>

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