[PATCH v4 6/7] iommu/dma: Centralise iommu_setup_dma_ops()

[Dmitry Baryshkov]

On Tue, 30 Apr 2024 at 01:26, Robin Murphy <robin.murphy at arm.com> wrote:
>
> On 2024-04-29 5:31 pm, Dmitry Baryshkov wrote:
> > On Fri, Apr 19, 2024 at 05:54:45PM +0100, Robin Murphy wrote:
> >> It's somewhat hard to see, but arm64's arch_setup_dma_ops() should only
> >> ever call iommu_setup_dma_ops() after a successful iommu_probe_device(),
> >> which means there should be no harm in achieving the same order of
> >> operations by running it off the back of iommu_probe_device() itself.
> >> This then puts it in line with the x86 and s390 .probe_finalize bodges,
> >> letting us pull it all into the main flow properly. As a bonus this lets
> >> us fold in and de-scope the PCI workaround setup as well.
> >>
> >> At this point we can also then pull the call up inside the group mutex,
> >> and avoid having to think about whether iommu_group_store_type() could
> >> theoretically race and free the domain if iommu_setup_dma_ops() ran just
> >> *before* iommu_device_use_default_domain() claims it... Furthermore we
> >> replace one .probe_finalize call completely, since the only remaining
> >> implementations are now one which only needs to run once for the initial
> >> boot-time probe, and two which themselves render that path unreachable.
> >>
> >> This leaves us a big step closer to realistically being able to unpick
> >> the variety of different things that iommu_setup_dma_ops() has been
> >> muddling together, and further streamline iommu-dma into core API flows
> >> in future.
> >>
> >> Reviewed-by: Lu Baolu <baolu.lu at linux.intel.com> # For Intel IOMMU
> >> Reviewed-by: Jason Gunthorpe <jgg at nvidia.com>
> >> Tested-by: Hanjun Guo <guohanjun at huawei.com>
> >> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> >> ---
> >> v2: Shuffle around to make sure the iommu_group_do_probe_finalize() case
> >>      is covered as well, with bonus side-effects as above.
> >> v3: *Really* do that, remembering the other two probe_finalize sites too.
> >> ---
> >>   arch/arm64/mm/dma-mapping.c  |  2 --
> >>   drivers/iommu/amd/iommu.c    |  8 --------
> >>   drivers/iommu/dma-iommu.c    | 18 ++++++------------
> >>   drivers/iommu/dma-iommu.h    | 14 ++++++--------
> >>   drivers/iommu/intel/iommu.c  |  7 -------
> >>   drivers/iommu/iommu.c        | 20 +++++++-------------
> >>   drivers/iommu/s390-iommu.c   |  6 ------
> >>   drivers/iommu/virtio-iommu.c | 10 ----------
> >>   include/linux/iommu.h        |  7 -------
> >>   9 files changed, 19 insertions(+), 73 deletions(-)
> >
> > This patch breaks UFS on Qualcomm SC8180X Primus platform:
> >
> >
> > [    3.846856] arm-smmu 15000000.iommu: Unhandled context fault: fsr=0x402, iova=0x1032db3e0, fsynr=0x130000, cbfrsynra=0x300, cb=4
>
> Hmm, a context fault implies that the device did get attached to a DMA
> domain, thus has successfully been through __iommu_probe_device(), yet
> somehow still didn't get the right DMA ops (since that "IOVA" looks more
> like a PA to me). Do you see the "Adding to IOMMU group..." message for
> this device, and/or any other relevant messages or errors before this
> point?

No, nothing relevant.

[    8.372395] ufshcd-qcom 1d84000.ufshc: Adding to iommu group 6

(please ignore the timestamp, it comes before ufshc being probed).

> I'm guessing there's a fair chance probe deferral might be
> involved as well. I'd like to understand what path(s) this ends up
> taking through __iommu_probe_device() and of_dma_configure(), or at
> least the number and order of probe attempts between the UFS and SMMU
> drivers.

__iommu_probe_device() gets called twice and returns early because ops is NULL.

Then finally of_dma_configure_id() is called. The following branches are taken:

np == dev->of_node
of_dma_get_range() returned 0
bus_dma_limit and dma_range_map are set
__iommu_probe_device() is called, using the `!group->default_domain &&
!group_lis` case, then group->default_domain() is not NULL,
In the end, iommu_setup_dma_ops() is called.

Then the ufshc probe defers (most likely the PHY is not present or
some other device is not there yet).

On the next (succeeding) try, of_dma_configure_id() is called again.
The call trace is more or less the same, except that
__iommu_probe_device() is not called

> I'll stare at the code in the morning and see if I can spot any
> overlooked ways in which what I think might be happening could happen,
> but any more info to help narrow it down would be much appreciated.
>
> Thanks,
> Robin.
>
> > [    3.846880] ufshcd-qcom 1d84000.ufshc: ufshcd_check_errors: saved_err 0x20000 saved_uic_err 0x0
> > [    3.846929] host_regs: 00000000: 1587031f 00000000 00000300 00000000
> > [    3.846935] host_regs: 00000010: 01000000 00010217 00000000 00000000
> > [    3.846941] host_regs: 00000020: 00000000 00070ef5 00000000 00000000
> > [    3.846946] host_regs: 00000030: 0000000f 00000001 00000000 00000000
> > [    3.846951] host_regs: 00000040: 00000000 00000000 00000000 00000000
> > [    3.846956] host_regs: 00000050: 032db000 00000001 00000000 00000000
> > [    3.846962] host_regs: 00000060: 00000000 80000000 00000000 00000000
> > [    3.846967] host_regs: 00000070: 032dd000 00000001 00000000 00000000
> > [    3.846972] host_regs: 00000080: 00000000 00000000 00000000 00000000
> > [    3.846977] host_regs: 00000090: 00000016 00000000 00000000 0000000c
> > [    3.847074] ufshcd-qcom 1d84000.ufshc: ufshcd_err_handler started; HBA state eh_fatal; powered 1; shutting down 0; saved_err = 131072; saved_uic_err = 0; force_reset = 0
> > [    4.406550] ufshcd-qcom 1d84000.ufshc: ufshcd_verify_dev_init: NOP OUT failed -11
> > [    4.417953] ufshcd-qcom 1d84000.ufshc: ufshcd_async_scan failed: -11
> >



-- 
With best wishes
Dmitry