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Tsirkin" To: Jocelyn Falempe Cc: linux-kernel@vger.kernel.org, David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Simona Vetter , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , dri-devel@lists.freedesktop.org, virtualization@lists.linux.dev, Eric Auger Subject: Re: [PATCH RFC] virtgpu: don't reset on shutdown Message-ID: <20250410084651-mutt-send-email-mst@kernel.org> References: <0d24e539766c9220b2380839472d1dc8739b5322.1744268995.git.mst@redhat.com> <07b30329-b4f0-4655-87fb-3ac52f9c64ff@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07b30329-b4f0-4655-87fb-3ac52f9c64ff@redhat.com> On Thu, Apr 10, 2025 at 02:33:26PM +0200, Jocelyn Falempe wrote: > On 10/04/2025 09:16, Michael S. Tsirkin wrote: > > It looks like GPUs are used by panic after shutdown is invoked. > > Thus, breaking virtio gpu in the shutdown callback is not a good idea - > > guest hangs attempting to flush out the panics, with this warnings: > > I don't think drm_panic is involved. In your backtrace, the warning > comes from virtio_gpu_queue_ctrl_sgs(), which is called by fbcon, using drm > fbdev emulation to draw the console. > > In case of drm_panic, it is the panic variant, > virtio_gpu_panic_queue_ctrl_sgs() which is called. > > Also the line number is for the centos-stream-9 kernel, which don't have the > "panic" variant of this function yet. > > > > > [ 20.504464] WARNING: CPU: 0 PID: 568 at drivers/gpu/drm/virtio/virtgpu_vq.c:358 virtio_gpu_queue_ctrl_sgs+0x236/0x290 [virtio_gpu] > > [ 20.505685] Modules linked in: 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 rfkill ip_set nf_tables nfnetlink vfat fat intel_rapl_msr intel_rapl_common intel_uncore_frequency_common nfit libnvdimm kvm_intel kvm rapl iTCO_wdt iTCO_vendor_support virtio_gpu virtio_dma_buf pcspkr drm_shmem_helper i2c_i801 drm_kms_helper lpc_ich i2c_smbus virtio_balloon joydev drm fuse xfs libcrc32c ahci libahci crct10dif_pclmul crc32_pclmul crc32c_intel libata virtio_net ghash_clmulni_intel net_failover virtio_blk failover serio_raw dm_mirror dm_region_hash dm_log dm_mod > > [ 20.511847] CPU: 0 PID: 568 Comm: kworker/0:3 Kdump: loaded Tainted: G W ------- --- 5.14.0-578.6675_1757216455.el9.x86_64 #1 > > [ 20.513157] Hardware name: Red Hat KVM/RHEL, BIOS edk2-20241117-3.el9 11/17/2024 > > [ 20.513918] Workqueue: events drm_fb_helper_damage_work [drm_kms_helper] > > [ 20.514626] RIP: 0010:virtio_gpu_queue_ctrl_sgs+0x236/0x290 [virtio_gpu] > > [ 20.515332] Code: 00 00 48 85 c0 74 0c 48 8b 78 08 48 89 ee e8 51 50 00 00 65 ff 0d 42 e3 74 3f 0f 85 69 ff ff ff 0f 1f 44 00 00 e9 5f ff ff ff <0f> 0b e9 3f ff ff ff 48 83 3c 24 00 74 0e 49 8b 7f 40 48 85 ff 74 > > [ 20.517272] RSP: 0018:ff34f0a8c0787ad8 EFLAGS: 00010282 > > [ 20.517820] RAX: 00000000fffffffb RBX: 0000000000000000 RCX: 0000000000000820 > > [ 20.518565] RDX: 0000000000000000 RSI: ff34f0a8c0787be0 RDI: ff218bef03a26300 > > [ 20.519308] RBP: ff218bef03a26300 R08: 0000000000000001 R09: ff218bef07224360 > > [ 20.520059] R10: 0000000000008dc0 R11: 0000000000000002 R12: ff218bef02630028 > > [ 20.520806] R13: ff218bef0263fb48 R14: ff218bef00cb8000 R15: ff218bef07224360 > > [ 20.521555] FS: 0000000000000000(0000) GS:ff218bef7ba00000(0000) knlGS:0000000000000000 > > [ 20.522397] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 20.522996] CR2: 000055ac4f7871c0 CR3: 000000010b9f2002 CR4: 0000000000771ef0 > > [ 20.523740] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [ 20.524477] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400 > > [ 20.525223] PKRU: 55555554 > > [ 20.525515] Call Trace: > > [ 20.525777] > > [ 20.526003] ? show_trace_log_lvl+0x1c4/0x2df > > [ 20.526464] ? show_trace_log_lvl+0x1c4/0x2df > > [ 20.526925] ? virtio_gpu_queue_fenced_ctrl_buffer+0x82/0x2c0 [virtio_gpu] > > [ 20.527643] ? virtio_gpu_queue_ctrl_sgs+0x236/0x290 [virtio_gpu] > > [ 20.528282] ? __warn+0x7e/0xd0 > > [ 20.528621] ? virtio_gpu_queue_ctrl_sgs+0x236/0x290 [virtio_gpu] > > [ 20.529256] ? report_bug+0x100/0x140 > > [ 20.529643] ? handle_bug+0x3c/0x70 > > [ 20.530010] ? exc_invalid_op+0x14/0x70 > > [ 20.530421] ? asm_exc_invalid_op+0x16/0x20 > > [ 20.530862] ? virtio_gpu_queue_ctrl_sgs+0x236/0x290 [virtio_gpu] > > [ 20.531506] ? virtio_gpu_queue_ctrl_sgs+0x174/0x290 [virtio_gpu] > > [ 20.532148] virtio_gpu_queue_fenced_ctrl_buffer+0x82/0x2c0 [virtio_gpu] > > [ 20.532843] virtio_gpu_primary_plane_update+0x3e2/0x460 [virtio_gpu] > > [ 20.533520] drm_atomic_helper_commit_planes+0x108/0x320 [drm_kms_helper] > > [ 20.534233] drm_atomic_helper_commit_tail+0x45/0x80 [drm_kms_helper] > > [ 20.534914] commit_tail+0xd2/0x130 [drm_kms_helper] > > [ 20.535446] drm_atomic_helper_commit+0x11b/0x140 [drm_kms_helper] > > [ 20.536097] drm_atomic_commit+0xa4/0xe0 [drm] > > [ 20.536588] ? __pfx___drm_printfn_info+0x10/0x10 [drm] > > [ 20.537162] drm_atomic_helper_dirtyfb+0x192/0x270 [drm_kms_helper] > > [ 20.537823] drm_fbdev_shmem_helper_fb_dirty+0x43/0xa0 [drm_shmem_helper] > > [ 20.538536] drm_fb_helper_damage_work+0x87/0x160 [drm_kms_helper] > > [ 20.539188] process_one_work+0x194/0x380 > > [ 20.539612] worker_thread+0x2fe/0x410 > > [ 20.540007] ? __pfx_worker_thread+0x10/0x10 > > [ 20.540456] kthread+0xdd/0x100 > > [ 20.540791] ? __pfx_kthread+0x10/0x10 > > [ 20.541190] ret_from_fork+0x29/0x50 > > [ 20.541566] > > [ 20.541802] ---[ end trace 0000000000000000 ]--- > > > > The warning is from here: > > No, it comes from > > static int virtio_gpu_queue_ctrl_sgs(struct virtio_gpu_device *vgdev, > struct virtio_gpu_vbuffer *vbuf, > struct virtio_gpu_fence *fence, > int elemcnt, > struct scatterlist **sgs, > int outcnt, > int incnt) > > > > /* For drm_panic */ > > static int virtio_gpu_panic_queue_ctrl_sgs(struct virtio_gpu_device *vgdev, > > struct virtio_gpu_vbuffer *vbuf, > > int elemcnt, > > struct scatterlist **sgs, > > int outcnt, > > int incnt) > > { > > struct virtqueue *vq = vgdev->ctrlq.vq; > > int ret; > > > > if (vgdev->has_indirect) > > elemcnt = 1; > > > > if (vq->num_free < elemcnt) > > return -ENOMEM; > > > > ret = virtqueue_add_sgs(vq, sgs, outcnt, incnt, vbuf, GFP_ATOMIC); > > WARN_ON(ret); > > > > vbuf->seqno = ++vgdev->ctrlq.seqno; > > trace_virtio_gpu_cmd_queue(vq, virtio_gpu_vbuf_ctrl_hdr(vbuf), vbuf->seqno); > > > > atomic_inc(&vgdev->pending_commands); > > > > return 0; > > } > > > > > > Add an option for drivers to bypass the common break+reset handling. > > As DRM is careful to flush/synchronize outstanding buffers, it looks like > > GPU can just have a NOP there. > > So it looks like the shutdown is called in the middle of console drawing, so > either wait for it to finish, or let drm handle the shutdown, like your > patch does. > > > > > Fixes: 8bd2fa086a04 ("virtio: break and reset virtio devices on device_shutdown()") > > Cc: Eric Auger > > Signed-off-by: Michael S. Tsirkin > > --- > > > > Can someone who knows more about DRM and shutdown please tell me if this > > is a good idea? Posting for testing and early feedback, completely > > untested. > > > > > > > > drivers/gpu/drm/virtio/virtgpu_drv.c | 9 +++++++++ > > drivers/virtio/virtio.c | 6 ++++++ > > include/linux/virtio.h | 3 +++ > > 3 files changed, 18 insertions(+) > > > > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c > > index 2d88e390feb4..210464146a9c 100644 > > --- a/drivers/gpu/drm/virtio/virtgpu_drv.c > > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c > > @@ -128,6 +128,14 @@ static void virtio_gpu_remove(struct virtio_device *vdev) > > drm_dev_put(dev); > > } > > +static void virtio_gpu_shutdown(struct virtio_device *vdev) > > +{ > > + /* > > + * GPU is used by drm panic after shutdown. > > Hopefully, there are no panic on shutdown. OK looks like you agree with the patch, but the comments and the commit log need to be fixed up? > > + * Do nothing here, opt out of device reset. > > + */ > > +} > > + > > static void virtio_gpu_config_changed(struct virtio_device *vdev) > > { > > struct drm_device *dev = vdev->priv; > > @@ -162,6 +170,7 @@ static struct virtio_driver virtio_gpu_driver = { > > .id_table = id_table, > > .probe = virtio_gpu_probe, > > .remove = virtio_gpu_remove, > > + .shutdown = virtio_gpu_shutdown, > > .config_changed = virtio_gpu_config_changed > > }; > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > index 150753c3b578..95d5d7993e5b 100644 > > --- a/drivers/virtio/virtio.c > > +++ b/drivers/virtio/virtio.c > > @@ -407,6 +407,12 @@ static void virtio_dev_shutdown(struct device *_d) > > if (!drv) > > return; > > + /* If the driver has its own shutdown method, use that. */ > > + if (drv->shutdown) { > > + drv->shutdown(dev); > > + return; > > + } > > + > > /* > > * Some devices get wedged if you kick them after they are > > * reset. Mark all vqs as broken to make sure we don't. > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > index 4d16c13d0df5..64cb4b04be7a 100644 > > --- a/include/linux/virtio.h > > +++ b/include/linux/virtio.h > > @@ -220,6 +220,8 @@ size_t virtio_max_dma_size(const struct virtio_device *vdev); > > * occurs. > > * @reset_done: optional function to call after transport specific reset > > * operation has finished. > > + * @shutdown: synchronize with the device on shutdown. If provided, replaces > > + * the virtio core implementation. > > */ > > struct virtio_driver { > > struct device_driver driver; > > @@ -237,6 +239,7 @@ struct virtio_driver { > > int (*restore)(struct virtio_device *dev); > > int (*reset_prepare)(struct virtio_device *dev); > > int (*reset_done)(struct virtio_device *dev); > > + void (*shutdown)(struct virtio_device *dev); > > }; > > #define drv_to_virtio(__drv) container_of_const(__drv, struct virtio_driver, driver) > > Best regards, > > -- > > Jocelyn