On Wed, May 27, 2020 at 09:31:30PM +0100, John Garry wrote: >> Thanks for having prepared and posted this new patch series. After v3 >> was posted and before v4 was posted I had a closer look at the IRQ core. >> My conclusions (which may be incorrect) are as follows: >> * The only function that sets the 'is_managed' member of struct >> irq_affinity_desc to 1 is irq_create_affinity_masks(). >> * There are two ways to cause that function to be called: setting the >> PCI_IRQ_AFFINITY flag when calling pci_alloc_irq_vectors_affinity() or >> passing the 'affd' argument. pci_alloc_irq_vectors() calls >> pci_alloc_irq_vectors_affinity(). >> * The following drivers pass an affinity domain argument when allocating >> interrupts: virtio_blk, nvme, be2iscsi, csiostor, hisi_sas, megaraid, >> mpt3sas, qla2xxx, virtio_scsi. >> * The following drivers set the PCI_IRQ_AFFINITY flag but do not pass an >> affinity domain: aacraid, hpsa, lpfc, smartqpi, virtio_pci_common. >> >> What is not clear to me is why managed interrupts are shut down if the >> last CPU in their affinity mask is shut down? Has it been considered to >> modify the IRQ core such that managed PCIe interrupts are assigned to >> another CPU if the last CPU in their affinity mask is shut down? > > I think Thomas answered that here already: > https://lore.kernel.org/lkml/alpine.DEB.2.21.1901291717370.1513@xxxxxxxxxxxxxxxxxxxxxxx/ > > (vector space exhaustion) Exactly.
