linux-kernel - RE: [PATCH 0/5] Share sva domains with all devices bound to a mm

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Message-ID: <BN9PR11MB527638E7361714F8AA5FD4448C12A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Wed, 9 Aug 2023 09:41:20 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Zhang, Tina" <tina.zhang@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        Michael Shavit <mshavit@...gle.com>
CC:     "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 0/5] Share sva domains with all devices bound to a mm

> From: Zhang, Tina <tina.zhang@...el.com>
> Sent: Tuesday, August 8, 2023 3:50 PM
> 
> A sva domain's lifetime begins with binding a device to a mm and ends
> by releasing all the bound devices from that sva domain. Technically,
> there could be more than one sva domain identified by the mm PASID for
> the use of bound devices issuing DMA transactions.

Could you elaborate it with some concrete examples which motivate
this change?

> 
> To support mm PASID 1:n with sva domains, each mm needs to keep both a
> reference list of allocated sva domains and the corresponding PASID.
> However, currently, mm struct only has one pasid field for sva usage,
> which is used to keep the info of an assigned PASID. That pasid field
> cannot provide sufficient info to build up the 1:n mapping between PASID
> and sva domains.
> 
> This patch-set fills the gap by adding an mm_iommu field[1], whose type is
> mm_iommu_data struct, to replace the old pasid field. The introduced
> mm_iommu_data struct keeps info of both a reference list of sva domains
> and an assigned PASID.
> 
> 
> [1]: https://lore.kernel.org/linux-iommu/ZIBxPd1%2FJCAle6yP@nvidia.com/
> 
> 
> The RFC version of this patch-set is here:
> https://lore.kernel.org/linux-iommu/20230707013441.365583-1-
> tina.zhang@...el.com/
> 
> Tina Zhang (5):
>   iommu: Add mm_get_pasid() helper function
>   iommu: Call helper function to get assigned pasid value
>   mm: Add structure to keep sva information
>   iommu: Support mm PASID 1:n with sva domains
>   mm: Deprecate pasid field
> 
>  arch/x86/kernel/traps.c                       |  2 +-
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   | 12 ++---
>  drivers/iommu/intel/svm.c                     |  8 +--
>  drivers/iommu/iommu-sva.c                     | 50 ++++++++++++-------
>  include/linux/iommu.h                         | 19 +++++--
>  include/linux/mm_types.h                      |  3 +-
>  kernel/fork.c                                 |  1 -
>  mm/init-mm.c                                  |  3 --
>  8 files changed, 58 insertions(+), 40 deletions(-)
> 
> --
> 2.17.1