On Mon, Dec 3, 2018 at 7:45 AM Robin Murphy <robin.murphy@xxxxxxx> wrote: > > Hi Rob, > > On 01/12/2018 16:53, Rob Clark 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. > > Does this crash still happen with 4.20-rc? Because as of 6af588fed391 it > really shouldn't. for this hw, I'm still on 4.19, although that does look like it would avoid the issue. > > 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. > > s/solved/worked around/ > > If you want a guarantee of actually getting a specific hardware context > allocated for a given domain, there needs to be code in the IOMMU driver > to understand and honour that. Implicitly depending on whatever happens > to fall out of current driver behaviour on current systems is not a real > solution. ok, fair.. but I'll settle for "works" in the absence of better options.. At some level, it would be nice to be able to optionally specify a context-bank in the iommu bindings. But not sure how to make that fit w/ cb allocated per domain. And I assume I'm the only one who has this problem? > > Fixes: 97890ba9289c dma-mapping: detect and configure IOMMU in of_dma_configure > > That's rather misleading, since the crash described above depends on at > least two other major changes which came long after that commit. Fair, when I realized it was the difference in where the iommu attaches between dpu1 (sdm845) and everything coming before, I should have removed the tag. BR, -R > It's not that I don't understand exactly what you want here - just that > this commit message isn't a coherent justification for that ;) > > > 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; > > + } > > Given that a default domain will already have been allocated by the time > we get here, regardless of whether we pretend of_iommu_configure() did > nothing, I'm puzzled as to how this change is 'solving' that aspect as > claimed :/ > > Is CONFIG_IOMMU_DEFAULT_PASSTHROUGH a sufficient workaround for msm at > the moment, or do you have other devices which do actually want > iommu_dma_ops? > > Robin. > > > + > > arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent); > > > > return 0; > >
