On Wed, Apr 03, 2019 at 04:35:11PM -0300, Rodrigo Siqueira wrote: > Hi, > > I’m working to add writeback support to vkms; you can see my current > patch at the end of this email (some prints highlight the issue that I’m > asking for help here). I’m using the Liviu Dudau and Brian Starkey IGT > patchset, which can be seen here: > https://patchwork.freedesktop.org/series/39229/. > > I’m stuck with a problem that happens in my vkms_wb_atomic_commit() > function, which is a helper function at drm_connector_helper_funcs. You > can see the full implementation of this function at the end of this > email, but here is the important part: > > struct drm_framebuffer *fb = conn_state->writeback_job->fb; > struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0); > struct vkms_gem_object *vkms_obj = drm_gem_to_vkms_gem(gem_obj); > > A few lines after this variable initialization, I try to make a memory > copy like this: > > memcpy(vkms_conn->writeback_vaddr, vkms_obj->vaddr, vkms_obj->gem.size); > > If I test my implementation with the subtest writeback-fb-id, everything > work as expected; for extra details, this is the dmesg output after this > test and with a debug print: > > => writeback-fb-id > > [Apr 3 11:30] CIFS: Attempting to mount //10.0.2.4/qemu > [ +1.601900] Console: switching to colour dummy device 80x25 > [ +0.000017] [IGT] kms_writeback: executing > [ +0.032532] [IGT] kms_writeback: starting subtest writeback-fb-id > [ +0.001932] VKMS_OBJ (1): Buff (1) - Vaddr (1) - Size = 1228800 - count = 1 > [ +0.050524] [IGT] kms_writeback: exiting, ret=0 > [ +0.005202] Console: switching to colour frame buffer device 100x37 > > In the above log, you can see the print info; notice that Vaddr is the > output of vkms_obj->vaddr (Vaddr -> vkms_obj->vaddr != NULL). On the > other hand, if I try the subtest writeback-check-output, something weird > happens in this function. Here is the dmesg output for this test: > > => writeback-check-output > > [ +29.911185] Console: switching to colour dummy device 80x25 > [ +0.000017] [IGT] kms_writeback: executing > [ +0.021289] [IGT] kms_writeback: starting subtest writeback-check-output > [ +0.016270] VKMS_OBJ (1): Buff (1) - Vaddr (0) - Size = 1228800 - count = 0 > [ +0.000005] BUG: unable to handle kernel NULL pointer dereference at > 0000000000000000 > [ +0.000004] #PF error: [normal kernel read fault] > [ +0.000001] PGD 0 P4D 0 > [ +0.000003] Oops: 0000 [#1] PREEMPT SMP PTI > [ +0.000002] CPU: 3 PID: 426 Comm: kms_writeback Not tainted > 5.0.0-VKMS-RULES+ #102 > [ +0.000002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > 1.12.0-20181126_142135-anatol 04/01/2014 > [ +0.000021] RIP: 0010:__memcpy+0x12/0x20 > [ +0.000002] Code: ff 0f 31 48 c1 e2 20 48 09 c2 48 31 d3 e9 79 ff ff ff 90 > 90 90 90 90 90 0f 1f 44 00 00 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 <f3> 48 > a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 f3 a4 > [ +0.000001] RSP: 0018:ffffadaf0098fbd8 EFLAGS: 00010246 > [ +0.000002] RAX: ffff9f1bf5400000 RBX: ffff9f1bfa28df00 RCX: > 0000000000025800 > [ +0.000001] RDX: 0000000000000000 RSI: 0000000000000000 RDI: > ffff9f1bf5400000 > [ +0.000001] RBP: 0000000000000001 R08: 00000017818788be R09: > ffffadaf0098fb60 > [ +0.000001] R10: ffff9f1bfffdc998 R11: ffffffffa25ec401 R12: > ffff9f1b777ff430 > [ +0.000001] R13: ffffffffc06558b8 R14: ffffffffc06853c0 R15: > ffffffffc0685520 > [ +0.000002] FS: 00007f2862deae80(0000) GS:ffff9f1bfc980000(0000) > knlGS:0000000000000000 > [ +0.000001] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ +0.000001] CR2: 0000000000000000 CR3: 00000000baf6c000 CR4: > 00000000000006e0 > [ +0.000004] Call Trace: > [ +0.000023] drm_atomic_helper_commit_modeset_enables+0x15d/0x1e0 > [drm_kms_helper] > [ +0.000028] drm_atomic_helper_commit_tail+0x31/0x60 [drm_kms_helper] > [ +0.000008] commit_tail+0x58/0x70 [drm_kms_helper] > [ +0.000008] drm_atomic_helper_commit+0x103/0x110 [drm_kms_helper] > [ +0.000040] drm_mode_atomic_ioctl+0x829/0x950 [drm] > [ +0.000012] ? drm_atomic_set_property+0x960/0x960 [drm] > [ +0.000029] drm_ioctl_kernel+0xb2/0xf0 [drm] > [ +0.000011] drm_ioctl+0x25f/0x3f0 [drm] > [ +0.000009] ? drm_atomic_set_property+0x960/0x960 [drm] > [ +0.000004] ? n_tty_open+0xa0/0xa0 > [ +0.000004] do_vfs_ioctl+0xa4/0x630 > [ +0.000003] ksys_ioctl+0x60/0x90 > [ +0.000003] ? ksys_write+0x4f/0xb0 > [ +0.000002] __x64_sys_ioctl+0x16/0x20 > [ +0.000003] do_syscall_64+0x5b/0x170 > [ +0.000003] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ +0.000002] RIP: 0033:0x7f286677580b > [ +0.000001] Code: 0f 1e fa 48 8b 05 55 b6 0c 00 64 c7 00 26 00 00 00 48 c7 > c0 ff > > Notice that Vaddr became NULL for some reason that I cannot understand.
Just missing the .prepare_writeback_job() hook? -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
