Den 19.02.2021 14.40, skrev Thomas Zimmermann: > Fixes a regression for udl and probably other USB-based drivers where > joining and mirroring displays fails. > > Joining displays requires importing a dma_buf from another DRM driver. > These devices don't support DMA and therefore have no DMA mask. Trying > to map imported buffers from a DMA-able memory zone fails with an error. > An example is shown below. > > [ 60.050199] ------------[ cut here ]------------ > [ 60.055092] WARNING: CPU: 0 PID: 1403 at kernel/dma/mapping.c:190 dma_map_sg_attrs+0x8f/0xc0 > [ 60.064331] Modules linked in: af_packet(E) rfkill(E) dmi_sysfs(E) intel_rapl_msr(E) intel_rapl_common(E) snd_hda_codec_realtek(E) snd_hda_codec_generic(E) ledtrig_audio(E) snd_hda_codec_hdmi(E) x86_pkg_temp_thermal(E) intel_powerclam) > [ 60.064801] wmi(E) video(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_intel(E) xor(E) raid6_pq(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) msr(E) efivarfs(E) > [ 60.170778] CPU: 0 PID: 1403 Comm: Xorg.bin Tainted: G E 5.11.0-rc5-1-default+ #747 > [ 60.179841] Hardware name: Dell Inc. OptiPlex 9020/0N4YC8, BIOS A24 10/24/2018 > [ 60.187145] RIP: 0010:dma_map_sg_attrs+0x8f/0xc0 > [ 60.191822] Code: 4d 85 ff 75 2b 49 89 d8 44 89 e1 44 89 f2 4c 89 ee 48 89 ef e8 62 30 00 00 85 c0 78 36 5b 5d 41 5c 41 5d 41 5e 41 5f c3 0f 0b <0f> 0b 31 c0 eb ed 49 8d 7f 50 e8 72 f5 2a 00 49 8b 47 50 49 89 d8 > [ 60.210770] RSP: 0018:ffffc90001d6fc18 EFLAGS: 00010246 > [ 60.216062] RAX: 0000000000000000 RBX: 0000000000000020 RCX: ffffffffb31e677b > [ 60.223274] RDX: dffffc0000000000 RSI: ffff888212c10600 RDI: ffff8881b08a9488 > [ 60.230501] RBP: ffff8881b08a9030 R08: 0000000000000020 R09: ffff888212c10600 > [ 60.237710] R10: ffffed10425820df R11: 0000000000000001 R12: 0000000000000000 > [ 60.244939] R13: ffff888212c10600 R14: 0000000000000008 R15: 0000000000000000 > [ 60.252155] FS: 00007f08ac2b2f00(0000) GS:ffff8887cbe00000(0000) knlGS:0000000000000000 > [ 60.260333] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 60.266150] CR2: 000055831c899be8 CR3: 000000015372e006 CR4: 00000000001706f0 > [ 60.273369] Call Trace: > [ 60.275845] drm_gem_map_dma_buf+0xb4/0x120 > [ 60.280089] dma_buf_map_attachment+0x15d/0x1e0 > [ 60.284688] drm_gem_prime_import_dev.part.0+0x5d/0x140 > [ 60.289984] drm_gem_prime_fd_to_handle+0x213/0x280 > [ 60.294931] ? drm_prime_destroy_file_private+0x30/0x30 > [ 60.300224] drm_ioctl_kernel+0x131/0x180 > [ 60.304291] ? drm_setversion+0x230/0x230 > [ 60.308366] ? drm_prime_destroy_file_private+0x30/0x30 > [ 60.313659] drm_ioctl+0x2f1/0x500 > [ 60.317118] ? drm_version+0x150/0x150 > [ 60.320903] ? lock_downgrade+0xa0/0xa0 > [ 60.324806] ? do_vfs_ioctl+0x5f4/0x680 > [ 60.328694] ? __fget_files+0x13e/0x210 > [ 60.332591] ? ioctl_fiemap.isra.0+0x1a0/0x1a0 > [ 60.337102] ? __fget_files+0x15d/0x210 > [ 60.340990] __x64_sys_ioctl+0xb9/0xf0 > [ 60.344795] do_syscall_64+0x33/0x80 > [ 60.348427] entry_SYSCALL_64_after_hwframe+0x44/0xa9 I'm working on a USB display driver and got the same splat (although from i915_gem_map_dma_buf) and silenced it using: ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64)); But I understand now that this is not the solution. Since the USB host controller can do DMA, would the following be an acceptable solution? static struct drm_gem_object *gud_gem_prime_import(struct drm_device *drm, struct dma_buf *dma_buf) { struct usb_device *usb = gud_to_usb_device(to_gud_device(drm)); drm_dbg_prime(drm, "usb->bus->controller=%s\n", dev_name(usb->bus->controller)); return drm_gem_prime_import_dev(drm, dma_buf, usb->bus->controller); } static const struct drm_driver gud_drm_driver = { .gem_prime_import = gud_gem_prime_import, }; Noralf. > [ 60.353542] RIP: 0033:0x7f08ac7b53cb > [ 60.357168] Code: 89 d8 49 8d 3c 1c 48 f7 d8 49 39 c4 72 b5 e8 1c ff ff ff 85 c0 78 ba 4c 89 e0 5b 5d 41 5c c3 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 75 ba 0c 00 f7 d8 64 89 01 48 > [ 60.376108] RSP: 002b:00007ffeabc89fc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > [ 60.383758] RAX: ffffffffffffffda RBX: 00007ffeabc8a00c RCX: 00007f08ac7b53cb > [ 60.390970] RDX: 00007ffeabc8a00c RSI: 00000000c00c642e RDI: 000000000000000d > [ 60.398221] RBP: 00000000c00c642e R08: 000055831c691d00 R09: 000055831b2ec010 > [ 60.405446] R10: 00007f08acf6ada0 R11: 0000000000000246 R12: 000055831c691d00 > [ 60.412667] R13: 000000000000000d R14: 00000000007e9000 R15: 0000000000000000 > [ 60.419903] irq event stamp: 672893 > [ 60.423441] hardirqs last enabled at (672913): [<ffffffffb31b796d>] console_unlock+0x44d/0x500 > [ 60.432230] hardirqs last disabled at (672922): [<ffffffffb31b7963>] console_unlock+0x443/0x500 > [ 60.441021] softirqs last enabled at (672940): [<ffffffffb46003dd>] __do_softirq+0x3dd/0x554 > [ 60.449634] softirqs last disabled at (672931): [<ffffffffb44010f2>] asm_call_irq_on_stack+0x12/0x20 > [ 60.458871] ---[ end trace f2f88696eb17806c ]--- > > For the fix, we don't call dma_map_sgtable() for devices without the > DMA mask. Drivers for such devices have to map the imported buffer into > kernel address space and perfom the copy operation in software. > > Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > > Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> > Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Cc: Johan Hovold <johan@xxxxxxxxxx> > Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > Cc: "Ahmed S. Darwish" <a.darwish@xxxxxxxxxxxxx> > Cc: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> > Cc: Oliver Neukum <oneukum@xxxxxxxx> > Cc: Felipe Balbi <balbi@xxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # v5.10+ > --- > drivers/gpu/drm/drm_prime.c | 27 ++++++++++++++++++--------- > 1 file changed, 18 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c > index 2a54f86856af..d5a39fe76b78 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -603,10 +603,15 @@ EXPORT_SYMBOL(drm_gem_map_detach); > * @attach: attachment whose scatterlist is to be returned > * @dir: direction of DMA transfer > * > - * Calls &drm_gem_object_funcs.get_sg_table and then maps the scatterlist. This > - * can be used as the &dma_buf_ops.map_dma_buf callback. Should be used together > + * Calls &drm_gem_object_funcs.get_sg_table and, if possible, maps the scatterlist. > + * This can be used as the &dma_buf_ops.map_dma_buf callback. Should be used together > * with drm_gem_unmap_dma_buf(). > * > + * Devices on some peripheral busses, such as USB, cannot use DMA. In this case, > + * pages in the scatterlist remain unmapped. Drivers for such devices should acquire > + * a mapping with dma_buf_vmap() and implement copy operation via bus-specific > + * interfaces. > + * > * Returns:sg_table containing the scatterlist to be returned; returns ERR_PTR > * on error. May return -EINTR if it is interrupted by a signal. > */ > @@ -627,12 +632,14 @@ struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, > if (IS_ERR(sgt)) > return sgt; > > - ret = dma_map_sgtable(attach->dev, sgt, dir, > - DMA_ATTR_SKIP_CPU_SYNC); > - if (ret) { > - sg_free_table(sgt); > - kfree(sgt); > - sgt = ERR_PTR(ret); > + if (attach->dev->dma_mask) { > + ret = dma_map_sgtable(attach->dev, sgt, dir, > + DMA_ATTR_SKIP_CPU_SYNC); > + if (ret) { > + sg_free_table(sgt); > + kfree(sgt); > + sgt = ERR_PTR(ret); > + } > } > > return sgt; > @@ -654,7 +661,9 @@ void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach, > if (!sgt) > return; > > - dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC); > + if (attach->dev->dma_mask) > + dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC); > + > sg_free_table(sgt); > kfree(sgt); > } > -- > 2.30.0 >