Am 27.04.22 um 17:39 schrieb Jason Gunthorpe:
On Wed, Apr 27, 2022 at 11:26:40AM -0400, Matthew Rosato wrote:
zPCI devices (zpci_dev) exist regardless of whether kvm is configured or
not, and you can e.g. bind the associated PCI device to vfio-pci when KVM is
not configured (or module not loaded) and get the existing vfio-pci-zdev
extensions for that device (extra VFIO_DEVICE_INFO response data). Making a
direct dependency on KVM would remove that; this was discussed in a prior
version because this extra info is not used today outside of a KVM usecase
are not specific to kvm that need vfio-pci-zdev).
I'm a bit confused, what is the drawback of just having a direct
symbol dependency here? It means vfio loads a little extra kernel
module code, but is that really a big worry given almost all vfio
users on s390 will be using it with kvm?
It's about trying to avoid loading unnecessary code (or at least giving a
way to turn it off).
Previously I did something like....
https://lore.kernel.org/kvm/20220204211536.321475-15-mjrosato@xxxxxxxxxxxxx/
And could do so again; as discussed in the thread there, I can use e.g.
CONFIG_VFIO_PCI_ZDEV_KVM and make vfio-pci-zdev depend on KVM in this
series. You only get the vfio-pci-zdev extensions when you configure KVM.
That make sense to me, I'd rather see that then the symbol_get/put here
I agree with Jason here.
