On Fri, Aug 24, 2012 at 07:59:06AM +0200, Jan Kiszka wrote: > On 2012-08-24 01:13, Cam Macdonell wrote: > > Hi Jan, > > > > I've bisected a bug in which MSI interrupts are not being delivered to > > the following patch, where msix_reset was moved in tot he PCI core. > > > > commit cbd2d4342b3d42ab33baa99f5b7a23491b5692f2 > > Author: Jan Kiszka <jan.kis...@siemens.com> > > Date: Tue May 15 20:09:56 2012 -0300 > > > > msi: Invoke msi/msix_reset from PCI core > > > > There is no point in pushing this burden to the devices, they tend to > > forget to call them (like intel-hda, ahci, xhci did). Instead, reset > > functions are now called from pci_device_reset. They do nothing if > > MSI/MSI-X is not in use. > > > > I've been debugging and it seems that when msix_notify() is triggered > > the second test in the "if" fails > > > > /* Send an MSI-X message */ > > void msix_notify(PCIDevice *dev, unsigned vector) > > { > > MSIMessage msg; > > > > if (vector >= dev->msix_entries_nr || !dev->msix_entry_used[vector]) > > return; > > > > … > > } > > > > here is some MSI-X debugging statements > > > > msix_init > > IVSHMEM: msix initialized (1 vectors) > > IVSHMEM: using vector 0 > > IVSHMEM: ivshmem_reset > > IVSHMEM: using vector 0 > > msix_reset > > msix_free_irq_entries 0x7fd52d1cea20 > > > > msix_free_irq_entries() sets dev->msix_entries_nr to 0, so I think it > > may be the cause. > > I suppose you mean it sets the msix_entry_used array to 0. > > > > > Shouldn't ivshmem's reset (which reenables the vectors) be triggered > > by the msix_reset? > > Actually, the whole msix vector usage tracking is useless today, this > just shows its downsides (in the absence of benefits). Megasas is > affected by this problem as well, virtio not as it calls msix_vector_use > during the configuration process the guest driver triggers. > > Two options: > - I can send my removal patch for msix_vector_use/unuse that I was > only planning for 1.3 so far, and we kill this pitfall earlier. > - We re-add msix_vector_use calls to the affected device models for > 1.2 and drop them later again for 1.3 when removing usage tracking. > [The third option to keep the usage tracking is a non-option for me. ;)] > > Michael?
Second option seems more prudent to me. Can you send a patch pls? > > > > Thanks, > > Cam > > > > p.s. And apologies, I should've caught this bug closer to that patch > > being merged. > > No problem. I should have seen this issue while changing the code. > > Jan > >