Messages in this thread | | | Subject | Re: [PATCH] PCI: Introduce flag for detached virtual functions | From | Matthew Rosato <> | Date | Wed, 12 Aug 2020 14:04:01 -0400 |
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On 8/12/20 12:43 PM, Alex Williamson wrote: > On Wed, 12 Aug 2020 10:50:17 -0400 > Matthew Rosato <mjrosato@linux.ibm.com> wrote: > >> s390x has the notion of providing VFs to the kernel in a manner >> where the associated PF is inaccessible other than via firmware. >> These are not treated as typical VFs and access to them is emulated >> by underlying firmware which can still access the PF. After >> abafbc55 however these detached VFs were no longer able to work >> with vfio-pci as the firmware does not provide emulation of the >> PCI_COMMAND_MEMORY bit. In this case, let's explicitly recognize >> these detached VFs so that vfio-pci can allow memory access to >> them again. >> >> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com> >> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com> >> Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com> >> --- >> arch/s390/pci/pci.c | 8 ++++++++ >> drivers/vfio/pci/vfio_pci_config.c | 3 ++- >> include/linux/pci.h | 1 + >> 3 files changed, 11 insertions(+), 1 deletion(-) >> >> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c >> index 3902c9f..04ac76d 100644 >> --- a/arch/s390/pci/pci.c >> +++ b/arch/s390/pci/pci.c >> @@ -581,6 +581,14 @@ int pcibios_enable_device(struct pci_dev *pdev, int mask) >> { >> struct zpci_dev *zdev = to_zpci(pdev); >> >> + /* >> + * If we have a VF on a non-multifunction bus, it must be a VF that is >> + * detached from its parent PF. We rely on firmware emulation to >> + * provide underlying PF details. >> + */ >> + if (zdev->vfn && !zdev->zbus->multifunction) >> + pdev->detached_vf = 1; >> + >> zpci_debug_init_device(zdev, dev_name(&pdev->dev)); >> zpci_fmb_enable_device(zdev); >> >> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c >> index d98843f..17845fc 100644 >> --- a/drivers/vfio/pci/vfio_pci_config.c >> +++ b/drivers/vfio/pci/vfio_pci_config.c >> @@ -406,7 +406,8 @@ bool __vfio_pci_memory_enabled(struct vfio_pci_device *vdev) >> * PF SR-IOV capability, there's therefore no need to trigger >> * faults based on the virtual value. >> */ >> - return pdev->is_virtfn || (cmd & PCI_COMMAND_MEMORY); >> + return pdev->is_virtfn || pdev->detached_vf || >> + (cmd & PCI_COMMAND_MEMORY); >> } >> >> /* > > Wouldn't we also want to enable the is_virtfn related code in > vfio_basic_config_read() and at least the initial setting of the > command register in vfio_config_init()? Otherwise we're extending the > incomplete emulation out to userspace. Thanks, >
We had discussed doing this internally and I ultimately left it out of this patch to keep the changes small... But I agree that it makes sense to fix the emulation for userspace. I can add the changes you suggest + would also need to change vfio_restore_bar() with:
- if (pdev->is_virtfn) + if (pdev->is_virtfn || pdev->detached_vf) return;
to prevent the config changes from tripping the restore code.
I'll send a V2 with this included.
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