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([2a01:e0a:f0e:9070:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43f20901c58sm30744735e9.0.2025.04.10.02.22.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Apr 2025 02:22:41 -0700 (PDT) Message-ID: <1beb29e4-0f11-4ed7-8096-436e0ac74679@redhat.com> Date: Thu, 10 Apr 2025 11:22:40 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC] virtgpu: don't reset on shutdown Content-Language: en-US To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Cc: David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Simona Vetter , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , dri-devel@lists.freedesktop.org, virtualization@lists.linux.dev References: <0d24e539766c9220b2380839472d1dc8739b5322.1744268995.git.mst@redhat.com> From: Eric Auger In-Reply-To: <0d24e539766c9220b2380839472d1dc8739b5322.1744268995.git.mst@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Michael, On 4/10/25 9:16 AM, 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: > > [ 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: > > /* 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. > > Fixes: 8bd2fa086a04 ("virtio: break and reset virtio devices on device_shutdown()") > Cc: Eric Auger > Signed-off-by: Michael S. Tsirkin This fixes the guest WARN_ON()/hangs for me. Reviewed-by: Eric Auger Tested-by: Eric Auger Thanks Eric > --- > > 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. > + * 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)