Messages in this thread | | | From | Angus Chen <> | Subject | RE: [PATCH v2] virtio_pci: avoid to request intx irq if pin is zero | Date | Wed, 28 Sep 2022 06:21:55 +0000 |
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> -----Original Message----- > From: Michael S. Tsirkin <mst@redhat.com> > Sent: Wednesday, September 28, 2022 1:59 PM > To: Angus Chen <angus.chen@jaguarmicro.com> > Cc: jasowang@redhat.com; virtualization@lists.linux-foundation.org; > linux-kernel@vger.kernel.org > Subject: Re: [PATCH v2] virtio_pci: avoid to request intx irq if pin is zero > > Thanks! More minor issues to address > > On Wed, Sep 28, 2022 at 01:35:22PM +0800, Angus Chen wrote: > > The background is that we use dpu in cloud computing,the arch is x86,80 > > cores.We will have a lots of virtio devices,like 512 or more. > > When we probe about 200 virtio_blk devices,it will fail and > > the stack is print as follows: > > > > [25338.485128] virtio-pci 0000:b3:00.0: virtio_pci: leaving for legacy driver > > [25338.496174] genirq: Flags mismatch irq 0. 00000080 (virtio418) vs. > 00015a00 (timer) > > [25338.503822] CPU: 20 PID: 5431 Comm: kworker/20:0 Kdump: loaded > Tainted: G OE --------- - - 4.18.0-305.30.1.el8.x86_64 > > [25338.516403] Hardware name: Inspur NF5280M5/YZMB-00882-10E, BIOS > 4.1.21 08/25/2021 > > [25338.523881] Workqueue: events work_for_cpu_fn > > [25338.528235] Call Trace: > > [25338.530687] dump_stack+0x5c/0x80 > > [25338.534000] __setup_irq.cold.53+0x7c/0xd3 > > [25338.538098] request_threaded_irq+0xf5/0x160 > > [25338.542371] vp_find_vqs+0xc7/0x190 > > [25338.545866] init_vq+0x17c/0x2e0 [virtio_blk] > > [25338.550223] ? ncpus_cmp_func+0x10/0x10 > > [25338.554061] virtblk_probe+0xe6/0x8a0 [virtio_blk] > > [25338.558846] virtio_dev_probe+0x158/0x1f0 > > [25338.562861] really_probe+0x255/0x4a0 > > [25338.566524] ? __driver_attach_async_helper+0x90/0x90 > > [25338.571567] driver_probe_device+0x49/0xc0 > > [25338.575660] bus_for_each_drv+0x79/0xc0 > > [25338.579499] __device_attach+0xdc/0x160 > > [25338.583337] bus_probe_device+0x9d/0xb0 > > [25338.587167] device_add+0x418/0x780 > > [25338.590654] register_virtio_device+0x9e/0xe0 > > [25338.595011] virtio_pci_probe+0xb3/0x140 > > [25338.598941] local_pci_probe+0x41/0x90 > > [25338.602689] work_for_cpu_fn+0x16/0x20 > > [25338.606443] process_one_work+0x1a7/0x360 > > [25338.610456] ? create_worker+0x1a0/0x1a0 > > [25338.614381] worker_thread+0x1cf/0x390 > > [25338.618132] ? create_worker+0x1a0/0x1a0 > > [25338.622051] kthread+0x116/0x130 > > [25338.625283] ? kthread_flush_work_fn+0x10/0x10 > > [25338.629731] ret_from_fork+0x1f/0x40 > > [25338.633395] virtio_blk: probe of virtio418 failed with error -16 > > > > The log : > > "genirq: Flags mismatch irq 0. 00000080 (virtio418) vs. 00015a00 (timer)" > > was print because of the irq 0 is used by timer exclusive,and when > > vp_find_vqs call vp_find_vqs_msix and return false twice for > > whatever reason,then it will call vp_find_vqs_intx for the last try. > > Because vp_dev->pci_dev->irq is zero,so it will be request irq 0 with > > flag IRQF_SHARED,we will get a backtrace like above. > > > > according to PCI spec , Devices (or device functions) > > that do not use an interrupt pin must put a 0 in this register. > > Pls add quotes and add "Interrupt Pin:" to make it clear in which register. > > > So if vp_dev->pci_dev->pin is zero, maybe we should not request legacy > > interrupt. > > and drop "maybe" here pls. I guess it sounds impolite to you but > as the patch author you get to make the tough decisions :) > > > > > Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com> > > Suggested-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > v2: > > - Decide whether to request an intx interrupt by pin instead of irq > > - suggested by mst > > > > > v1:https://lore.kernel.org/virtualization/20220928000228-mutt-send-email-mst > @kernel.org/T/#u > > > > drivers/virtio/virtio_pci_common.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/virtio/virtio_pci_common.c > b/drivers/virtio/virtio_pci_common.c > > index ad258a9d3b9f..81225e503e69 100644 > > --- a/drivers/virtio/virtio_pci_common.c > > +++ b/drivers/virtio/virtio_pci_common.c > > @@ -362,6 +362,9 @@ static int vp_find_vqs_intx(struct virtio_device *vdev, > unsigned int nvqs, > > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > > int i, err, queue_idx = 0; > > > > + if (vp_dev->pci_dev->pin == 0) > > + return -EINVAL; > > + > > Pls use !pin for brevity. Yes,that looks better. > > > vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL); > > if (!vp_dev->vqs) > > return -ENOMEM; > > > So, this is mostly ok. The only issue is this: > > > int vp_find_vqs(struct virtio_device *vdev, unsigned int nvqs, > struct virtqueue *vqs[], vq_callback_t *callbacks[], > const char * const names[], const bool *ctx, > struct irq_affinity *desc) > { > int err; > > /* Try MSI-X with one vector per queue. */ > err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true, ctx, > desc); > if (!err) > return 0; > /* Fallback: MSI-X with one vector for config, one shared for queues. > */ > err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, > desc); > if (!err) > return 0; > /* Finally fall back to regular interrupts. */ > return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names, ctx); > } > > > So the real source of failure to use msix, will be overwritten in err by EINVAL. > > How about moving the "if" to vp_find_vqs? > E.g. > /* Is there an interrupt pin? If not give up. */ > if (!vdev->pci_dev->pin) > return err; > OK. vp_find_vqs_intx is staic and it only be called by vp_find_vqs, and it will avoids a single press into the stack . I will send this in another version. > > > -- > > 2.17.1
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