> Hej,
>
> debug dma code is not happy with virtio gpu (arm64 VM):
>
> [ 305.881733] ------------[ cut here ]------------
> [ 305.883117] DMA-API: virtio-pci 0000:07:00.0: mapping sg segment longer
> than device claims to support [len=262144] [max=65536]
> [ 305.885976] WARNING: CPU: 8 PID: 2002 at kernel/dma/debug.c:1177
> check_sg_segment+0x2d0/0x420
> [ 305.888038] Modules linked in: crct10dif_ce(+) polyval_ce polyval_generic
> ghash_ce virtio_gpu(+) virtio_net net_failover virtio_blk(+) virtio_dma_buf
> virtio_console failover virtio_mmio scsi_dh_r dac scsi_dh_emc scsi_dh_alua
> dm_multipath qemu_fw_cfg
> [ 305.893496] CPU: 8 PID: 2002 Comm: (udev-worker) Not tainted 6.7.0 #1
> [ 305.895070] Hardware name: QEMU KVM Virtual Machine, BIOS edk2-
> 20230524-3.fc37 05/24/2023
> [ 305.897112] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS
> BTYPE=--)
> [ 305.897129] pc : check_sg_segment+0x2d0/0x420
> [ 305.897139] lr : check_sg_segment+0x2d0/0x420
> [ 305.897145] sp : ffff80008ffc69d0
> [ 305.897149] x29: ffff80008ffc69d0 x28: dfff800000000000 x27:
> ffffb0232879e578
> [ 305.897167] x26: ffffffff00000000 x25: ffffb0232778c060 x24:
> ffff19ee9b2060c0
> [ 305.897181] x23: 00000000ffffffff x22: ffffb0232ab9ce10 x21:
> ffff19eece5c64ac
> [ 305.906942] x20: 0000000000010000 x19: ffff19eece5c64a0 x18:
> ffff19eec36fc304
> [ 305.908633] x17: 6e61687420726567 x16: 6e6f6c20746e656d x15:
> 6765732067732067
> [ 305.910352] x14: 00000000f1f1f1f1 x13: 0000000000000001 x12:
> ffff700011ff8cc3
> [ 305.912044] x11: 1ffff00011ff8cc2 x10: ffff700011ff8cc2 x9 :
> ffffb02324a70e54
> [ 305.913751] x8 : 00008fffee00733e x7 : ffff80008ffc6617 x6 :
> 0000000000000001
> [ 305.915451] x5 : ffff80008ffc6610 x4 : 1fffe33e70564622 x3 :
> dfff800000000000
> [ 305.917158] x2 : 0000000000000000 x1 : 0000000000000000 x0 :
> ffff19f382b23100
> [ 305.918864] Call trace:
> [ 305.919474] check_sg_segment+0x2d0/0x420
> [ 305.920443] debug_dma_map_sg+0x2a0/0x428
> [ 305.921402] __dma_map_sg_attrs+0xf4/0x1a8
> [ 305.922388] dma_map_sgtable+0x7c/0x100
> [ 305.923318] drm_gem_shmem_get_pages_sgt+0x15c/0x328
> [ 305.924500]
> virtio_gpu_object_shmem_init.constprop.0.isra.0+0x50/0x628 [virtio_gpu]
> [ 305.926390] virtio_gpu_object_create+0x198/0x478 [virtio_gpu]
> [ 305.927802] virtio_gpu_mode_dumb_create+0x2a0/0x4c8 [virtio_gpu]
> [ 305.929272] drm_mode_create_dumb+0x1c0/0x280
> [ 305.930327] drm_client_framebuffer_create+0x140/0x328
> [ 305.931555] drm_fbdev_generic_helper_fb_probe+0x1bc/0x5c0
> [ 305.932871] __drm_fb_helper_initial_config_and_unlock+0x1e0/0x630
> [ 305.934372] drm_fb_helper_initial_config+0x50/0x68
> [ 305.935540] drm_fbdev_generic_client_hotplug+0x148/0x200
> [ 305.936819] drm_client_register+0x130/0x200
> [ 305.937856] drm_fbdev_generic_setup+0xe8/0x320
> [ 305.938932] virtio_gpu_probe+0x13c/0x2d0 [virtio_gpu]
> [ 305.940190] virtio_dev_probe+0x38c/0x600
> [ 305.941153] really_probe+0x334/0x9c8
> [ 305.942047] __driver_probe_device+0x164/0x3d8
> [ 305.943102] driver_probe_device+0x64/0x180
> [ 305.944094] __driver_attach+0x1d4/0x488
> [ 305.945045] bus_for_each_dev+0x104/0x198
> [ 305.946008] driver_attach+0x44/0x68
> [ 305.946892] bus_add_driver+0x23c/0x4a8
> [ 305.947838] driver_register+0xf8/0x3d0
> [ 305.948770] register_virtio_driver+0x74/0xc8
> [ 305.949836] virtio_gpu_driver_init+0x20/0xff8 [virtio_gpu]
> [ 305.951237] do_one_initcall+0x17c/0x8c0
> [ 305.952182] do_init_module+0x1dc/0x630
> [ 305.953106] load_module+0x10c0/0x1638
> [ 305.954012] init_module_from_file+0xe0/0x140
> [ 305.955058] idempotent_init_module+0x2c0/0x590
> [ 305.956174] __arm64_sys_finit_module+0xb4/0x140
> [ 305.957282] invoke_syscall+0xd8/0x258
> [ 305.958187] el0_svc_common.constprop.0+0x16c/0x240
> [ 305.959526] do_el0_svc+0x48/0x68
> [ 305.960456] el0_svc+0x58/0x118
> [ 305.961310] el0t_64_sync_handler+0x120/0x130
> [ 305.962510] el0t_64_sync+0x194/0x198
> [ 305.963509] irq event stamp: 37944
> [ 305.964412] hardirqs last enabled at (37943): [<ffffb02324a7439c>]
> console_unlock+0x1a4/0x1c8
> [ 305.966602] hardirqs last disabled at (37944): [<ffffb023276724e4>]
> el1_dbg+0x24/0xa0
> [ 305.968535] softirqs last enabled at (37930): [<ffffb0232475114c>]
> __do_softirq+0x8e4/0xe1c
> [ 305.970781] softirqs last disabled at (37925): [<ffffb0232475a9b0>]
> ____do_softirq+0x18/0x30
> [ 305.972937] ---[ end trace 0000000000000000 ]---
>
> The 64K max_segment size of the device seems to be inherited by PCIs
> default.
> The sg list is crated via this drm helper:
>
> struct sg_table *drm_prime_pages_to_sg(struct drm_device *dev,
> struct page **pages, unsigned int
> nr_pages)
> {
> ...
> if (dev)
> max_segment = dma_max_mapping_size(dev->dev);
> if (max_segment == 0)
> max_segment = UINT_MAX;
> err = sg_alloc_table_from_pages_segment(sg, pages, nr_pages, 0,
> nr_pages << PAGE_SHIFT,
> max_segment, GFP_KERNEL);
> ...
> }
>
> I'm a bit puzzled why this uses dma_max_mapping_size() and not
> dma_get_max_seg_size(). But since this is used by a lot of drivers
> I'm not really keen to touch this code that works like this for ages.
>
> So let's just make debug dma code aware of the actual segment size
> that's used by the device:
>
> --->8
> drm/virtio: set segment size for virtio_gpu device
>
> Set the segment size of the virtio_gpu device to the value
> used by the drm helpers when allocating sg lists to fix the
> following complaint from DMA_API debug code:
> DMA-API: virtio-pci 0000:07:00.0: mapping sg segment longer than device
> claims to support [len=262144] [max=65536]
>
> Signed-off-by: Sebastian Ott <sebott@xxxxxxxxxx>
> ---
> drivers/gpu/drm/virtio/virtgpu_drv.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c
> b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index 4334c7608408..74b2cb3295af 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -94,6 +94,7 @@ static int virtio_gpu_probe(struct virtio_device *vdev)
> goto err_free;
> }
>
> + dma_set_max_seg_size(dev->dev, dma_max_mapping_size(dev-
> >dev) ? : UINT_MAX);
Acked-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
> ret = virtio_gpu_init(vdev, dev);
> if (ret)
> goto err_free;
> --
> 2.43.0
>
>
