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Fri, 13 Jun 2025 04:55:26 -0700 (PDT) Received: from fedora ([94.73.34.56]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e22460bsm52636405e9.6.2025.06.13.04.55.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jun 2025 04:55:25 -0700 (PDT) Date: Fri, 13 Jun 2025 13:55:22 +0200 From: =?iso-8859-1?Q?Jos=E9_Exp=F3sito?= To: Thomas Zimmermann Cc: Simona Vetter , Greg KH , Jonathan.Cameron@huawei.com, airlied@gmail.com, aleksander.lobakin@intel.com, andriy.shevchenko@linux.intel.com, bhelgaas@google.com, broonie@kernel.org, dakr@kernel.org, dri-devel@lists.freedesktop.org, hamohammed.sa@gmail.com, lgirdwood@gmail.com, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, louis.chauvet@bootlin.com, lukas@wunner.de, lyude@redhat.com, maarten.lankhorst@linux.intel.com, mairacanal@riseup.net, melissa.srw@gmail.com, mripard@kernel.org, quic_zijuhu@quicinc.com, rafael@kernel.org, robin.murphy@arm.com, rust-for-linux@vger.kernel.org, simona@ffwll.ch Subject: Re: [PATCH v4 9/9] drm/vkms: convert to use faux_device Message-ID: References: <2025022643-scouting-petticoat-492b@gregkh> <20250311172054.2903-1-jose.exposito89@gmail.com> <2025031218-oxidize-backing-e278@gregkh> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Hi Thomas, Thanks for the heads up, this issue fall through the cracks. On Fri, Jun 13, 2025 at 10:15:05AM +0200, Thomas Zimmermann wrote: > Hi > > Am 13.03.25 um 18:20 schrieb José Expósito: > > On Thu, Mar 13, 2025 at 03:22:21PM +0100, Simona Vetter wrote: > > > On Wed, Mar 12, 2025 at 07:22:07AM +0100, Greg KH wrote: > > > > On Tue, Mar 11, 2025 at 06:20:53PM +0100, José Expósito wrote: > > > > > Hi everyone, > > > > > > > > > > > On Tue, Feb 25, 2025 at 02:51:40PM +0100, Louis Chauvet wrote: > > > > > > > > > > > > > > Le 25/02/2025 à 12:41, Thomas Zimmermann a écrit : > > > > > > > > Hi > > > > > > > > > > > > > > > > Am 10.02.25 um 15:37 schrieb Louis Chauvet: > > > > > > > > > On 10/02/25 - 13:30, Greg Kroah-Hartman wrote: > > > > > > > > > > The vkms driver does not need to create a platform device, as there is > > > > > > > > > > no real platform resources associated it, it only did so because it was > > > > > > > > > > simple to do that in order to get a device to use for resource > > > > > > > > > > management of drm resources. Change the driver to use the faux device > > > > > > > > > > instead as this is NOT a real platform device. > > > > > > > > > > > > > > > > > > > > Cc: Louis Chauvet > > > > > > > > > > Cc: Haneen Mohammed > > > > > > > > > > Cc: Simona Vetter > > > > > > > > > > Cc: Melissa Wen > > > > > > > > > > Cc: Maarten Lankhorst > > > > > > > > > > Cc: Maxime Ripard > > > > > > > > > > Cc: Thomas Zimmermann > > > > > > > > > > Cc: David Airlie > > > > > > > > > > Cc: dri-devel@lists.freedesktop.org > > > > > > > > > > Reviewed-by: Lyude Paul > > > > > > > > > > Signed-off-by: Greg Kroah-Hartman > > > > > > > > Reviewed-by: Thomas Zimmermann > > > > > > > > > > > > > > > > > Tested-by: Louis Chauvet > > > > > > > > > Reviewed-by: Louis Chauvet > > > > > > > > > > > > > > > > > > Thanks for the modification, it seems to work. > > > > > > > > Should this patch be merged through DRM trees? drm-misc-next is at > > > > > > > > v6.14-rc4 and has struct faux_device. > > > > > > > Hi, > > > > > > > > > > > > > > I was not aware the faux-device was merged, as it is a new feature, I > > > > > > > expected it to reach drm-misc-next on 6.15-rc1. > > > > > > I added it to Linus's tree just so that DRM could get these changes into > > > > > > their tree now :) > > > > > > > > > > > > > I plan to merge [1] today/tomorrow (well tested with platform_device), and > > > > > > > then I will submit an updated version of this patch (only trivial conflicts, > > > > > > > but never tested with multiple VKMS devices). > > > > > > > > > > > > > > [1]:https://lore.kernel.org/all/20250218101214.5790-1-jose.exposito89@gmail.com/ > > > > > > Great, thanks! > > > > > > > > > > > > greg k-h > > > > > Testing this patch again as part of some IGT tests I'm working on, > > > > > I noticed that, applying this patch on top of the latest drm-misc-next > > > > > triggers a warning at drivers/gpu/drm/drm_gem.c:571, in > > > > > drm_gem_get_pages(): > > > > > > > > > >     if (WARN_ON(!obj->filp)) > > > > >             return ERR_PTR(-EINVAL); > > > > I don't see how the faux bus change would have anything to do with a > > > > filp as that's not related as far as I can tell. But I don't know the > > > > drm layer at all, where does that filp come from? > > > Yeah that filp is the shmem file that backs gem bo. That's very far away > > > from anything device/driver related datastrctures. If this is a new > > > failure due to the aux bux conversion then it would be really surprising. > > Agreed, I find it surprising, but reverting the patch removes the warning. > > > > It's most likely an issue on my side, but I decided to double check just > > in case someone else is also seeing this warning. > > Any news on this issue? I tested again with drm-misc-next. At the moment of writing this, the last commit is 6bd90e700b42 ("drm/xe: Make dma-fences compliant with the safe access rules") and I still see a similar warning. The stack trace changed, but the warning is still present. I'm going to detail the exact steps I followed. Let's see if someone else is able to reproduce the issue: I started by applying the patches from this series that are not already merged: - [PATCH v4 4/9] x86/microcode: move away from using a fake platform - [PATCH v4 5/9] wifi: cfg80211: move away from using a fake - [PATCH v4 8/9] drm/vgem/vgem_drv convert to use faux_device - [PATCH v4 9/9] drm/vkms: convert to use faux_device The last patch has small conflict in vkms_drv.h that I solved like this: struct vkms_device { struct drm_device drm; struct faux_device *faux_dev; const struct vkms_config *config; }; And in vkms_drv.c: static int vkms_create(struct vkms_config *config) { int ret; struct faux_device *fdev; struct vkms_device *vkms_device; const char *dev_name; dev_name = vkms_config_get_device_name(config); fdev = faux_device_create(dev_name, NULL, NULL); if (!fdev) return -ENODEV; Next, I installed the new kernel in a QEMU virtual machine running Fedora 41. There is nothing special about my Fedora, it is the regular desktop version. After a reboot, "sudo modprobe vkms" shows a similar warning in dmesg. For reference, the warning is at the end of my email. Am I the only one sawing this warning? Jose --- [ 69.417850] [drm] Initialized vkms 1.0.0 for vkms on minor 1 [ 69.419446] faux_driver vkms: [drm] fb1: vkmsdrmfb frame buffer device [ 69.520944] ------------[ cut here ]------------ [ 69.520954] WARNING: CPU: 2 PID: 1015 at drivers/dma-buf/dma-buf.c:1518 dma_buf_vmap+0x212/0x540 [ 69.520992] Modules linked in: vkms snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables rfkill qrtr sunrpc binfmt_misc ppdev pktcdvd parport_pc parport pcspkr i2c_piix4 e1000 i2c_smbus joydev loop nfnetlink vsock_loopback zram vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vmw_vmci vsock bochs serio_raw ata_generic pata_acpi fuse qemu_fw_cfg [ 69.521082] CPU: 2 UID: 42 PID: 1015 Comm: KMS thread Not tainted 6.16.0-rc1+ #3 PREEMPT(voluntary) [ 69.521092] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.fc42 04/01/2014 [ 69.521095] RIP: 0010:dma_buf_vmap+0x212/0x540 [ 69.521105] Code: 7c 41 ff 03 0f 85 0a 02 00 00 c9 e9 c8 47 0c 01 80 3c 06 00 0f 85 c4 01 00 00 48 c7 01 00 00 00 00 48 85 d2 0f 85 bd fe ff ff <0f> 0b b8 ea ff ff ff eb af 48 85 f6 0f 85 cf 01 00 00 48 89 4c 24 [ 69.521112] RSP: 0018:ffffc90006a5f690 EFLAGS: 00010246 [ 69.521125] RAX: dffffc0000000000 RBX: 1ffff92000d4beea RCX: ffff88811467dcc8 [ 69.521128] RDX: 0000000000000000 RSI: 1ffff110228cfb99 RDI: ffff88811467dcd0 [ 69.521131] RBP: ffffc90006a5f728 R08: 1ffff92000d4bed9 R09: fffff52000d4bef1 [ 69.521162] R10: fffff52000d4bef2 R11: ffff8881017f4e28 R12: ffff8881149594f0 [ 69.521165] R13: ffff888114959400 R14: 1ffff11023146b29 R15: ffff88811467dcc8 [ 69.521168] FS: 00007fbbdd1ff6c0(0000) GS:ffff888417580000(0000) knlGS:0000000000000000 [ 69.521172] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 69.521174] CR2: 00007fbbcc0345c8 CR3: 000000011ec5a000 CR4: 00000000000006f0 [ 69.521179] Call Trace: [ 69.521182] [ 69.521185] ? __pfx_dma_buf_vmap+0x10/0x10 [ 69.521193] ? dma_resv_get_singleton+0x9a/0x2a0 [ 69.521197] drm_gem_shmem_vmap_locked+0xc2/0x5f0 [ 69.521208] ? __pfx_drm_gem_shmem_vmap_locked+0x10/0x10 [ 69.521212] ? __pfx_ww_mutex_lock+0x10/0x10 [ 69.521225] ? sched_clock_noinstr+0xd/0x20 [ 69.521230] ? local_clock_noinstr+0x13/0xf0 [ 69.521233] drm_gem_shmem_object_vmap+0xd/0x20 [ 69.521237] drm_gem_vmap_locked+0x70/0xf0 [ 69.521247] drm_gem_vmap+0x4c/0xa0 [ 69.521250] drm_gem_fb_vmap+0xb2/0x3b0 [ 69.521255] vkms_prepare_fb+0x6f/0x90 [vkms] [ 69.521264] ? drm_atomic_helper_setup_commit+0xb7b/0x1320 [ 69.521268] drm_atomic_helper_prepare_planes+0x19f/0xb90 [ 69.521272] ? __pfx_drm_atomic_helper_commit+0x10/0x10 [ 69.521276] drm_atomic_helper_commit+0x126/0x2d0 [ 69.521279] ? __pfx_drm_atomic_helper_commit+0x10/0x10 [ 69.521282] drm_atomic_commit+0x205/0x2d0 [ 69.521290] ? _raw_spin_lock_irqsave+0x97/0xf0 [ 69.521295] ? __pfx_drm_atomic_commit+0x10/0x10 [ 69.521299] ? __pfx___drm_printfn_info+0x10/0x10 [ 69.521313] ? drm_event_reserve_init+0x1cd/0x260 [ 69.521318] drm_mode_atomic_ioctl+0x1c79/0x2d30 [ 69.521323] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10 [ 69.521326] ? __kasan_check_write+0x18/0x20 [ 69.521339] drm_ioctl_kernel+0x17b/0x2f0 [ 69.521343] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10 [ 69.521349] ? __pfx_drm_ioctl_kernel+0x10/0x10 [ 69.521353] ? __pfx_do_vfs_ioctl+0x10/0x10 [ 69.521361] ? __kasan_check_write+0x18/0x20 [ 69.521365] drm_ioctl+0x51b/0xbd0 [ 69.521369] ? __pfx_drm_mode_atomic_ioctl+0x10/0x10 [ 69.521373] ? __pfx_drm_ioctl+0x10/0x10 [ 69.521378] ? selinux_file_ioctl+0xfc/0x260 [ 69.521390] __x64_sys_ioctl+0x143/0x1d0 [ 69.521394] x64_sys_call+0xf4b/0x1d70 [ 69.521404] do_syscall_64+0x82/0x2a0 [ 69.521408] ? __kasan_check_write+0x18/0x20 [ 69.521411] ? do_user_addr_fault+0x491/0xa60 [ 69.521420] ? irqentry_exit+0x3f/0x50 [ 69.521423] ? exc_page_fault+0x8b/0xe0 [ 69.521426] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 69.521430] RIP: 0033:0x7fbc078fd8ed [ 69.521441] Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00 [ 69.521444] RSP: 002b:00007fbbdd1fd9b0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 69.521449] RAX: ffffffffffffffda RBX: 00007fbbcc02af60 RCX: 00007fbc078fd8ed [ 69.521452] RDX: 00007fbbdd1fda50 RSI: 00000000c03864bc RDI: 0000000000000035 [ 69.521455] RBP: 00007fbbdd1fda00 R08: 00000000000000e0 R09: 0000000000000001 [ 69.521457] R10: 0000000000000003 R11: 0000000000000246 R12: 00007fbbdd1fda50 [ 69.521459] R13: 00000000c03864bc R14: 0000000000000035 R15: 00007fbbcc02acf0 [ 69.521464] [ 69.521466] ---[ end trace 0000000000000000 ]--- > Best regards > Thomas > > > > > Jose > > > > > -Sima > > > > > > -- > > > Simona Vetter > > > Software Engineer, Intel Corporation > > > http://blog.ffwll.ch > > -- > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Frankenstrasse 146, 90461 Nuernberg, Germany > GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman > HRB 36809 (AG Nuernberg) >