Re: [PATCH v7 0/9] ACPI/IORT: Support for IORT RMR node

[Ard Biesheuvel <ardb@kernel.org>]

On Thu, 5 Aug 2021 at 15:35, Shameerali Kolothum Thodi
<shameerali.kolothum.thodi@huawei.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Ard Biesheuvel [mailto:ardb@kernel.org]
> > Sent: 05 August 2021 14:23
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> > Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>; ACPI Devel Maling List
> > <linux-acpi@vger.kernel.org>; Linux IOMMU
> > <iommu@lists.linux-foundation.org>; Linuxarm <linuxarm@huawei.com>;
> > Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>; Joerg Roedel
> > <joro@8bytes.org>; Robin Murphy <robin.murphy@arm.com>; Will Deacon
> > <will@kernel.org>; wanghuiqiang <wanghuiqiang@huawei.com>; Guohanjun
> > (Hanjun Guo) <guohanjun@huawei.com>; Steven Price
> > <steven.price@arm.com>; Sami Mujawar <Sami.Mujawar@arm.com>; Jon
> > Nettleton <jon@solid-run.com>; Eric Auger <eric.auger@redhat.com>;
> > yangyicong <yangyicong@huawei.com>
> > Subject: Re: [PATCH v7 0/9] ACPI/IORT: Support for IORT RMR node
> >
> > On Thu, 5 Aug 2021 at 10:10, Shameer Kolothum
> > <shameerali.kolothum.thodi@huawei.com> wrote:
> > >
> > > Hi,
> > >
> > > The series adds support to IORT RMR nodes specified in IORT
> > > Revision E.b -ARM DEN 0049E[0]. RMR nodes are used to describe
> > > memory ranges that are used by endpoints and require a unity
> > > mapping in SMMU.
> > >
> > > We have faced issues with 3408iMR RAID controller cards which
> > > fail to boot when SMMU is enabled. This is because these
> > > controllers make use of host memory for various caching related
> > > purposes and when SMMU is enabled the iMR firmware fails to
> > > access these memory regions as there is no mapping for them.
> > > IORT RMR provides a way for UEFI to describe and report these
> > > memory regions so that the kernel can make a unity mapping for
> > > these in SMMU.
> > >
> >
> > Does this mean we are ignoring the RMR memory ranges, and exposing the
> > entire physical address space to devices using the stream IDs in
> > question?
>
> Nope. RMR node is used to describe the memory ranges used by end points
> behind SMMU. And this information is used to create 1 : 1 mappings for those
> ranges in SMMU. Anything outside those ranges will result in translation
> fault(if there are no other dynamic DMA mappings).
>

Excellent! It was not obvious to me from looking at the patches, so I
had to ask.

Thanks,
Ard.

>
> >
> > > Change History:
> > >
> > > v6 --> v7
> > >
> > > The only change from v6 is the fix pointed out by Steve to
> > > the SMMUv2 SMR bypass install in patch #8.
> > >
> > > Thanks to the Tested-by tags by Laurentiu with SMMUv2 and
> > > Hanjun/Huiqiang with SMMUv3 for v6. I haven't added the tags
> > > yet as the series still needs more review[1].
> > >
> > > Feedback and tests on this series is very much appreciated.
> > >
> > > v5 --> v6
> > > - Addressed comments from Robin & Lorenzo.
> > >   : Moved iort_parse_rmr() to acpi_iort_init() from
> > >     iort_init_platform_devices().
> > >   : Removed use of struct iort_rmr_entry during the initial
> > >     parse. Using struct iommu_resv_region instead.
> > >   : Report RMR address alignment and overlap errors, but continue.
> > >   : Reworked arm_smmu_init_bypass_stes() (patch # 6).
> > > - Updated SMMUv2 bypass SMR code. Thanks to Jon N (patch #8).
> > > - Set IOMMU protection flags(IOMMU_CACHE, IOMMU_MMIO) based
> > >   on Type of RMR region. Suggested by Jon N.
> > >
> > > Thanks,
> > > Shameer
> > > [0] https://developer.arm.com/documentation/den0049/latest/
> > > [1]
> > https://lore.kernel.org/linux-acpi/20210716083442.1708-1-shameerali.koloth
> > um.thodi@huawei.com/T/#m043c95b869973a834b2fd57f3e1ed0325c84f3b7
> > > ------
> > > v4 --> v5
> > >  -Added a fw_data union to struct iommu_resv_region and removed
> > >   struct iommu_rmr (Based on comments from Joerg/Robin).
> > >  -Added iommu_put_rmrs() to release mem.
> > >  -Thanks to Steve for verifying on SMMUv2, but not added the Tested-by
> > >   yet because of the above changes.
> > >
> > > v3 -->v4
> > > -Included the SMMUv2 SMR bypass install changes suggested by
> > >  Steve(patch #7)
> > > -As per Robin's comments, RMR reserve implementation is now
> > >  more generic  (patch #8) and dropped v3 patches 8 and 10.
> > > -Rebase to 5.13-rc1
> > >
> > > RFC v2 --> v3
> > >  -Dropped RFC tag as the ACPICA header changes are now ready to be
> > >   part of 5.13[0]. But this series still has a dependency on that patch.
> > >  -Added IORT E.b related changes(node flags, _DSM function 5 checks for
> > >   PCIe).
> > >  -Changed RMR to stream id mapping from M:N to M:1 as per the spec and
> > >   discussion here[1].
> > >  -Last two patches add support for SMMUv2(Thanks to Jon Nettleton!)
> > > ------
> > >
> > > Jon Nettleton (1):
> > >   iommu/arm-smmu: Get associated RMR info and install bypass SMR
> > >
> > > Shameer Kolothum (8):
> > >   iommu: Introduce a union to struct iommu_resv_region
> > >   ACPI/IORT: Add support for RMR node parsing
> > >   iommu/dma: Introduce generic helper to retrieve RMR info
> > >   ACPI/IORT: Add a helper to retrieve RMR memory regions
> > >   iommu/arm-smmu-v3: Introduce strtab init helper
> > >   iommu/arm-smmu-v3: Refactor arm_smmu_init_bypass_stes() to force
> > >     bypass
> > >   iommu/arm-smmu-v3: Get associated RMR info and install bypass STE
> > >   iommu/dma: Reserve any RMR regions associated with a dev
> > >
> > >  drivers/acpi/arm64/iort.c                   | 172
> > +++++++++++++++++++-
> > >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c |  76 +++++++--
> > >  drivers/iommu/arm/arm-smmu/arm-smmu.c       |  48 ++++++
> > >  drivers/iommu/dma-iommu.c                   |  89 +++++++++-
> > >  include/linux/acpi_iort.h                   |   7 +
> > >  include/linux/dma-iommu.h                   |  13 ++
> > >  include/linux/iommu.h                       |  11 ++
> > >  7 files changed, 393 insertions(+), 23 deletions(-)
> > >
> > > --
> > > 2.17.1
> > >
> > >
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