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SubjectRe: [PATCH] of/device: add blacklist for iommu dma_ops
On Sat, Dec 1, 2018 at 8:54 AM Rob Clark <robdclark@gmail.com> 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@chromium.org>
> Signed-off-by: Rob Clark <robdclark@gmail.com>
> ---
> 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@chromium.org>

Best regards,
Tomasz

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