On Thu, 10 Dec 2020 10:13:29 -0500
Matthew Rosato <mjros...@linux.ibm.com> wrote:
> On 12/10/20 5:28 AM, Cornelia Huck wrote:
> > On Wed, 9 Dec 2020 15:34:20 -0500
> > Matthew Rosato <mjros...@linux.ibm.com> wrote:
> >
> >> s390 PCI currently disallows PCI devices without the MSI-X capability.
> >> However, this fence doesn't make sense for passthrough devices. Move
> >> the check to only fence emulated devices (e.g., virtio).
> >>
> >> Signed-off-by: Matthew Rosato <mjros...@linux.ibm.com>
> >> Reviewed-by: Pierre Morel <pmo...@linux.ibm.com>
> >> ---
> >> hw/s390x/s390-pci-bus.c | 14 ++++++++------
> >> 1 file changed, 8 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> >> index 05f7460..afad048 100644
> >> --- a/hw/s390x/s390-pci-bus.c
> >> +++ b/hw/s390x/s390-pci-bus.c
> >> @@ -1028,12 +1028,12 @@ static void s390_pcihost_plug(HotplugHandler
> >> *hotplug_dev, DeviceState *dev,
> >> s390_pci_get_clp_info(pbdev);
> >> } else {
> >> pbdev->fh |= FH_SHM_EMUL;
> >> - }
> >>
> >> - if (s390_pci_msix_init(pbdev)) {
> >> - error_setg(errp, "MSI-X support is mandatory "
> >> - "in the S390 architecture");
> >> - return;
> >> + if (s390_pci_msix_init(pbdev)) {
> >> + error_setg(errp, "MSI-X support is mandatory "
> >> + "in the S390 architecture");
> >> + return;
> >> + }
> >> }
> >>
> >> if (dev->hotplugged) {
> >> @@ -1073,7 +1073,9 @@ static void s390_pcihost_unplug(HotplugHandler
> >> *hotplug_dev, DeviceState *dev,
> >> devfn = pci_dev->devfn;
> >> qdev_unrealize(dev);
> >>
> >> - s390_pci_msix_free(pbdev);
> >> + if (pbdev->fh & FH_SHM_EMUL) {
> >> + s390_pci_msix_free(pbdev);
> >> + }
> >> s390_pci_iommu_free(s, bus, devfn);
> >> pbdev->pdev = NULL;
> >> pbdev->state = ZPCI_FS_RESERVED;
> >
> > Remind me: Wasn't it only msi that was strictly required (i.e., not msi-x?)
> >
> > Can we generally relax this requirement, possibly with some changes in
> > the adapter interrupt mapping? I might misremember, though.
> >
>
> Yes, but even so our current emulation support only sets up for MSI-X,
> it does not have an msi_init() equivalent. I do believe that this
> requirement can be relaxed at some point for the emulation support as
> well, but the focus on this set was to at least stop fencing passthrough
> for no reason.
Looking back to when this was introduced, I see that 857cc71985dc
("s390x/pci: merge msix init functions") actually makes this mandatory
and states that nothing changes for passthrough. Has anything changed
regarding msi-x in the architecture in the meantime?
