Messages in this thread | | | Date | Fri, 17 Jun 2022 18:15:39 +0200 | Subject | Re: [PATCH v9 10/21] vfio/pci: introduce CONFIG_VFIO_PCI_ZDEV_KVM | From | Thomas Huth <> |
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On 14/06/2022 10.56, Pierre Morel wrote: > > > On 6/8/22 15:15, Matthew Rosato wrote: >> On 6/8/22 2:19 AM, Thomas Huth wrote: >>> On 06/06/2022 22.33, Matthew Rosato wrote: >>>> The current contents of vfio-pci-zdev are today only useful in a KVM >>>> environment; let's tie everything currently under vfio-pci-zdev to >>>> this Kconfig statement and require KVM in this case, reducing complexity >>>> (e.g. symbol lookups). >>>> >>>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com> > > Reviewed-by: Pierre Morel <pmorel@linux.ibm.com> > > >>>> --- >>>> drivers/vfio/pci/Kconfig | 11 +++++++++++ >>>> drivers/vfio/pci/Makefile | 2 +- >>>> include/linux/vfio_pci_core.h | 2 +- >>>> 3 files changed, 13 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig >>>> index 4da1914425e1..f9d0c908e738 100644 >>>> --- a/drivers/vfio/pci/Kconfig >>>> +++ b/drivers/vfio/pci/Kconfig >>>> @@ -44,6 +44,17 @@ config VFIO_PCI_IGD >>>> To enable Intel IGD assignment through vfio-pci, say Y. >>>> endif >>>> +config VFIO_PCI_ZDEV_KVM >>>> + bool "VFIO PCI extensions for s390x KVM passthrough" >>>> + depends on S390 && KVM >>>> + default y >>>> + help >>>> + Support s390x-specific extensions to enable support for enhancements >>>> + to KVM passthrough capabilities, such as interpretive execution of >>>> + zPCI instructions. >>>> + >>>> + To enable s390x KVM vfio-pci extensions, say Y. >>> >>> Is it still possible to disable CONFIG_VFIO_PCI_ZDEV_KVM ? Looking at the >>> later patches (e.g. 20/21 where you call kvm_s390_pci_zpci_op() from >>> kvm-s390.c), it rather seems to me that it currently cannot be disabled >>> independently (as long as KVM is enabled). >> >> Yes, you can build with, for example, CONFIG_VFIO_PCI_ZDEV_KVM=n and >> CONFIG_KVM=m -- I tested it again just now. The result is kvm and >> vfio-pci are built and vfio-pci works, but none of the vfio-pci-zdev >> extensions are available (including zPCI interpretation). >> >> This is accomplished via the placement of some IS_ENABLED checks. Some >> calls (e.g. AEN init) are fenced by IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM). >> There are also some areas that are fenced off via a call to >> kvm_s390_pci_interp_allowed() which also includes an IS_ENABLED check >> along with checks for facility and cpu id. >> >> Using patch 20 as an example, KVM_CAP_S390_ZPCI_OP will always be reported >> as unavailable to userspace if CONFIG_VFIO_PCI_ZDEV_KVM=n due to the call >> to kvm_s390_pci_interp_allowed(). If userspace sends us the ioctl anyway, >> we will return -EINVAL because there is again a >> IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM) check before we read the ioctl args >> from userspace. > > Yes and the code will not be generated by the compiler in patch 20 after the > break if CONFIG_VFIO_PCI_ZDEV_KVM is not enabled. > > + case KVM_S390_ZPCI_OP: { > + struct kvm_s390_zpci_op args; > + > + r = -EINVAL; > + if (!IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)) > + break; > > Code not generated----v > > + if (copy_from_user(&args, argp, sizeof(args))) { > + r = -EFAULT; > + break; > + } > + r = kvm_s390_pci_zpci_op(kvm, &args); > + break; > > ----------^
OK, good to know, thanks for the clarification!
Thomas
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