[PATCH] drm/prime: Only call dma_map_sgtable() for devices with DMA support
Christian König
christian.koenig at amd.com
Fri Feb 19 14:43:19 UTC 2021
Am 19.02.21 um 15:34 schrieb Thomas Zimmermann:
> Hi
>
> Am 19.02.21 um 14:45 schrieb Christian König:
>> Well as far as I can see this is a relative clear NAK.
>>
>> When a device can't do DMA and has no DMA mask then why it is
>> requesting an sg-table in the first place?
>>
>> The problem is rather in drm_gem_prime_import_dev() which always
>> tries to create an sg-table to get a GEM object, even when the device
>> doesn't support DMA at all.
>
> Sure, that's the clean solution. But it also needs a bit of work on
> the way the importing works. Our generic code assumes that an SG table
> is being used. Most driver's memory managers as well, I guess.
>
> The regressing patch has already been in upstream kernels for a while.
> The fix at hand is backport-able at least.
>
> Can we add a TODO item for the real thing?
Not really.
The "fix" here is a hack for the export handling code in DRM. That only
works because the USB device tries to communicate with another DRM
driver, but is not a general solution you could backport.
What you can do instead for example to fix this is to implement the
gem_prime_import callback in the USB device so that the GEM object is
created without trying to get an sg-table without being DMA capable.
Regards,
Christian.
>
> Best regards
> Thomas
>
>>
>> Regards,
>> Christian.
>>
>> Am 19.02.21 um 14:40 schrieb 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
>>> [ 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 at suse.de>
>>> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB
>>> devices")
>>> Cc: Christoph Hellwig <hch at lst.de>
>>> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>>> Cc: Alan Stern <stern at rowland.harvard.edu>
>>> Cc: Johan Hovold <johan at kernel.org>
>>> Cc: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
>>> Cc: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
>>> Cc: "Ahmed S. Darwish" <a.darwish at linutronix.de>
>>> Cc: Mathias Nyman <mathias.nyman at linux.intel.com>
>>> Cc: Oliver Neukum <oneukum at suse.com>
>>> Cc: Felipe Balbi <balbi at kernel.org>
>>> Cc: Thomas Gleixner <tglx at linutronix.de>
>>> Cc: <stable at vger.kernel.org> # 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
>>>
>>
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