Re: [PATCH] of/device: add blacklist for iommu dma_ops

[Vivek Gautam]

On Mon, Jun 3, 2019 at 4:14 PM Rob Clark <robdclark@xxxxxxxxx> wrote:
>
> On Mon, Jun 3, 2019 at 12:57 AM Vivek Gautam
> <vivek.gautam@xxxxxxxxxxxxxx> wrote:
> >
> >
> >
> > On 6/3/2019 11:50 AM, Tomasz Figa wrote:
> > > On Mon, Jun 3, 2019 at 4:40 AM Rob Clark <robdclark@xxxxxxxxx> wrote:
> > >> On Fri, May 10, 2019 at 7:35 AM Rob Clark <robdclark@xxxxxxxxx> wrote:
> > >>> On Tue, Dec 4, 2018 at 2:29 PM Rob Herring <robh+dt@xxxxxxxxxx> wrote:
> > >>>> On Sat, Dec 1, 2018 at 10:54 AM Rob Clark <robdclark@xxxxxxxxx> wrote:
> > >>>>> This solves a problem we see with drm/msm, caused by getting
> > >>>>> iommu_dma_ops while we attach our own domain and manage it directly at
> > >>>>> the iommu API level:
> > >>>>>
> > >>>>>    [0000000000000038] user address but active_mm is swapper
> > >>>>>    Internal error: Oops: 96000005 [#1] PREEMPT SMP
> > >>>>>    Modules linked in:
> > >>>>>    CPU: 7 PID: 70 Comm: kworker/7:1 Tainted: G        W         4.19.3 #90
> > >>>>>    Hardware name: xxx (DT)
> > >>>>>    Workqueue: events deferred_probe_work_func
> > >>>>>    pstate: 80c00009 (Nzcv daif +PAN +UAO)
> > >>>>>    pc : iommu_dma_map_sg+0x7c/0x2c8
> > >>>>>    lr : iommu_dma_map_sg+0x40/0x2c8
> > >>>>>    sp : ffffff80095eb4f0
> > >>>>>    x29: ffffff80095eb4f0 x28: 0000000000000000
> > >>>>>    x27: ffffffc0f9431578 x26: 0000000000000000
> > >>>>>    x25: 00000000ffffffff x24: 0000000000000003
> > >>>>>    x23: 0000000000000001 x22: ffffffc0fa9ac010
> > >>>>>    x21: 0000000000000000 x20: ffffffc0fab40980
> > >>>>>    x19: ffffffc0fab40980 x18: 0000000000000003
> > >>>>>    x17: 00000000000001c4 x16: 0000000000000007
> > >>>>>    x15: 000000000000000e x14: ffffffffffffffff
> > >>>>>    x13: ffff000000000000 x12: 0000000000000028
> > >>>>>    x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f
> > >>>>>    x9 : 0000000000000000 x8 : ffffffc0fab409a0
> > >>>>>    x7 : 0000000000000000 x6 : 0000000000000002
> > >>>>>    x5 : 0000000100000000 x4 : 0000000000000000
> > >>>>>    x3 : 0000000000000001 x2 : 0000000000000002
> > >>>>>    x1 : ffffffc0f9431578 x0 : 0000000000000000
> > >>>>>    Process kworker/7:1 (pid: 70, stack limit = 0x0000000017d08ffb)
> > >>>>>    Call trace:
> > >>>>>     iommu_dma_map_sg+0x7c/0x2c8
> > >>>>>     __iommu_map_sg_attrs+0x70/0x84
> > >>>>>     get_pages+0x170/0x1e8
> > >>>>>     msm_gem_get_iova+0x8c/0x128
> > >>>>>     _msm_gem_kernel_new+0x6c/0xc8
> > >>>>>     msm_gem_kernel_new+0x4c/0x58
> > >>>>>     dsi_tx_buf_alloc_6g+0x4c/0x8c
> > >>>>>     msm_dsi_host_modeset_init+0xc8/0x108
> > >>>>>     msm_dsi_modeset_init+0x54/0x18c
> > >>>>>     _dpu_kms_drm_obj_init+0x430/0x474
> > >>>>>     dpu_kms_hw_init+0x5f8/0x6b4
> > >>>>>     msm_drm_bind+0x360/0x6c8
> > >>>>>     try_to_bring_up_master.part.7+0x28/0x70
> > >>>>>     component_master_add_with_match+0xe8/0x124
> > >>>>>     msm_pdev_probe+0x294/0x2b4
> > >>>>>     platform_drv_probe+0x58/0xa4
> > >>>>>     really_probe+0x150/0x294
> > >>>>>     driver_probe_device+0xac/0xe8
> > >>>>>     __device_attach_driver+0xa4/0xb4
> > >>>>>     bus_for_each_drv+0x98/0xc8
> > >>>>>     __device_attach+0xac/0x12c
> > >>>>>     device_initial_probe+0x24/0x30
> > >>>>>     bus_probe_device+0x38/0x98
> > >>>>>     deferred_probe_work_func+0x78/0xa4
> > >>>>>     process_one_work+0x24c/0x3dc
> > >>>>>     worker_thread+0x280/0x360
> > >>>>>     kthread+0x134/0x13c
> > >>>>>     ret_from_fork+0x10/0x18
> > >>>>>    Code: d2800004 91000725 6b17039f 5400048a (f9401f40)
> > >>>>>    ---[ end trace f22dda57f3648e2c ]---
> > >>>>>    Kernel panic - not syncing: Fatal exception
> > >>>>>    SMP: stopping secondary CPUs
> > >>>>>    Kernel Offset: disabled
> > >>>>>    CPU features: 0x0,22802a18
> > >>>>>    Memory Limit: none
> > >>>>>
> > >>>>> The problem is that when drm/msm does it's own iommu_attach_device(),
> > >>>>> now the domain returned by iommu_get_domain_for_dev() is drm/msm's
> > >>>>> domain, and it doesn't have domain->iova_cookie.
> > >>>>>
> > >>>>> We kind of avoided this problem prior to sdm845/dpu because the iommu
> > >>>>> was attached to the mdp node in dt, which is a child of the toplevel
> > >>>>> mdss node (which corresponds to the dev passed in dma_map_sg()).  But
> > >>>>> with sdm845, now the iommu is attached at the mdss level so we hit the
> > >>>>> iommu_dma_ops in dma_map_sg().
> > >>>>>
> > >>>>> But auto allocating/attaching a domain before the driver is probed was
> > >>>>> already a blocking problem for enabling per-context pagetables for the
> > >>>>> GPU.  This problem is also now solved with this patch.
> > >>>>>
> > >>>>> Fixes: 97890ba9289c dma-mapping: detect and configure IOMMU in of_dma_configure
> > >>>>> Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> > >>>>> Signed-off-by: Rob Clark <robdclark@xxxxxxxxx>
> > >>>>> ---
> > >>>>> This is an alternative/replacement for [1].  What it lacks in elegance
> > >>>>> it makes up for in practicality ;-)
> > >>>>>
> > >>>>> [1] https://patchwork.freedesktop.org/patch/264930/
> > >>>>>
> > >>>>>   drivers/of/device.c | 22 ++++++++++++++++++++++
> > >>>>>   1 file changed, 22 insertions(+)
> > >>>>>
> > >>>>> diff --git a/drivers/of/device.c b/drivers/of/device.c
> > >>>>> index 5957cd4fa262..15ffee00fb22 100644
> > >>>>> --- a/drivers/of/device.c
> > >>>>> +++ b/drivers/of/device.c
> > >>>>> @@ -72,6 +72,14 @@ int of_device_add(struct platform_device *ofdev)
> > >>>>>          return device_add(&ofdev->dev);
> > >>>>>   }
> > >>>>>
> > >>>>> +static const struct of_device_id iommu_blacklist[] = {
> > >>>>> +       { .compatible = "qcom,mdp4" },
> > >>>>> +       { .compatible = "qcom,mdss" },
> > >>>>> +       { .compatible = "qcom,sdm845-mdss" },
> > >>>>> +       { .compatible = "qcom,adreno" },
> > >>>>> +       {}
> > >>>>> +};
> > >>>> Not completely clear to whether this is still needed or not, but this
> > >>>> really won't scale. Why can't the driver for these devices override
> > >>>> whatever has been setup by default?
> > >>>>
> > >>> fwiw, at the moment it is not needed, but it will become needed again
> > >>> to implement per-context pagetables (although I suppose for this we
> > >>> only need to blacklist qcom,adreno and not also the display nodes).
> > >> So, another case I've come across, on the display side.. I'm working
> > >> on handling the case where bootloader enables display (and takes iommu
> > >> out of reset).. as soon as DMA domain gets attached we get iommu
> > >> faults, because bootloader has already configured display for scanout.
> > >> Unfortunately this all happens before actual driver is probed and has
> > >> a chance to intervene.
> >
> > Things are bad for MTP sdm845 too where the bootloader sets up iommu to
> > display splash screen, and when the kernel resets the iommu, the mappings go
> > for a toss resulting in fatal faults.
> > Bjorn was working on something recently to address this. Adding him to
> > the thread.
> >
>
> yeah, I was hitting it on the yoga c630 laptop, but it is the identical problem.
>
> We'd worked around it so far with a hack in arm-smmu to temporarily
> ioremap the display controller block and disable INTF1, which is
> *defn* not a good solution ;-)

Right, but this doesn't always work for MTP. I believe Bjorn has something
more inline with downstream.

Regards
>
> BR,
> -R
>
> >
> > Best regards
> > Vivek
> >
> > >> It's rather unfortunate that we tried to be clever rather than just
> > >> making drivers call some function to opt-in to the hookup of dma iommu
> > >> ops :-(
> > > I think it still works for the 90% of cases and if 10% needs some
> > > explicit work in the drivers, that's better than requiring 100% of the
> > > drivers to do things manually.
> > >
> > > Adding Marek who had the same problem on Exynos.
> > >
> > > Best regards,
> > > Tomasz
> > >
> > >> BR,
> > >> -R
> > >>
> > >>> The reason is that in the current state the core code creates the
> > >>> first domain before the driver has a chance to intervene and tell it
> > >>> not to.  And this results that driver ends up using a different
> > >>> context bank on the iommu than what the firmware expects.
> > >>>
> > >>> I guess the alternative is to put some property in DT.. but that
> > >>> doesn't really feel right.  I guess there aren't really many (or any?)
> > >>> other drivers that have this specific problem, so I don't really
> > >>> expect it to be a scaling problem.
> > >>>
> > >>> Yeah, it's a bit ugly, but I'll take a small ugly working hack, over
> > >>> elegant but non-working any day ;-)... but if someone has a better
> > >>> idea then I'm all ears.
> > >>>
> > >>> BR,
> > >>> -R
> >
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