linux-kernel - Re: [RFC v3 00/10] KVM PCIe/MSI passthrough on ARM/ARM64 and IOVA reserved regions

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Date:   Thu, 8 Dec 2016 10:36:55 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, christoffer.dall@...aro.org,
        marc.zyngier@....com, robin.murphy@....com,
        alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
        tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org
Cc:     kvm@...r.kernel.org, drjones@...hat.com,
        linux-kernel@...r.kernel.org, pranav.sawargaonkar@...il.com,
        iommu@...ts.linux-foundation.org, punit.agrawal@....com,
        diana.craciun@....com, Don Dutile <ddutile@...hat.com>
Subject: Re: [RFC v3 00/10] KVM PCIe/MSI passthrough on ARM/ARM64 and IOVA
 reserved regions

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
   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.
   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(-)
>