On Wed, Sep 28, 2022 at 11:45:45AM +0200, Christoph Hellwig wrote: > On Tue, Sep 27, 2022 at 04:47:20PM -0400, Michael S. Tsirkin wrote: > > > 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 called vp_find_vqs_msix and return false twice,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. > > > > First this is a bug. We can fix that so it will fail more cleanly. > > > > We should check pci_dev->pin and if 0 do not try to use INT#x > > at all. > > It will still fail, just with a nicer backtrace. > > How do we end up with a pci_dev without a valid PIN? This patch is broken but there's no v3 which looks right, and includes an explanation. > Btw, that whole > vp_find_* code looks extremely fucked up to me. The whole point of > pci_alloc_irq_vectors* API is that it keeps drivers from poling into > details of MSI-X v MSI vs INTX. Poking? I think that code predates that, a minimal change was made to support affinity... but again, it does not look like the main issue has anything to do with that. Or maybe I'm wrong ... > > - because of auto affinity, we try to reserve an interrupt on all CPUs > > - as there are 512 devices with a single vector per VQ we would > > have no issue as they would be spread between CPUs, > > but allocating on all CPUs fails. > > > > > > I don't think the issue should be fixed at blk level - it is not > > blk specifix - but yes this looks like a problem. > > Christoph, any idea? > > I think this goes into the low-level interrupt vector allocator. I think > Thomas is still the expert on it. syzbot is also telling us there's an issue in next (and not due to virtio changes - I intentionally removed most of them for a while and the issue was there) but I could not figure it out. -- MST
