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

[Tomasz Figa]

On Sat, Dec 1, 2018 at 8:54 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" },
> +       {}
> +};
> +
>  /**
>   * of_dma_configure - Setup DMA configuration
>   * @dev:       Device to apply DMA configuration
> @@ -164,6 +172,20 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
>         dev_dbg(dev, "device is%sbehind an iommu\n",
>                 iommu ? " " : " not ");
>
> +       /*
> +        * There is at least one case where the driver wants to directly
> +        * manage the IOMMU, but if we end up with iommu dma_ops, that
> +        * interferes with the drivers ability to use dma_map_sg() for
> +        * cache operations.  Since we don't currently have a better
> +        * solution, and this code runs before the driver is probed and
> +        * has a chance to intervene, use a simple blacklist to avoid
> +        * ending up with iommu dma_ops:
> +        */
> +       if (of_match_device(iommu_blacklist, dev)) {
> +               dev_dbg(dev, "skipping iommu hookup\n");
> +               iommu = NULL;
> +       }
> +
>         arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
>
>         return 0;
> --
> 2.19.2
>

+Marek Szyprowski who I believe had a similar problem with Exynos DRM before.

Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>

Best regards,
Tomasz