I'm working in QEMU, and attempting to see if the guest can still use a PCI device without the corresponding kernel module loaded.
To start, lspci -v shows the following:
00:01.3 Bridge: Intel Corporation ########## PIIX4 ACPI (rev 03)
Subsystem: Red Hat, Inc Qemu virtual machine
Flags: medium devsel, IRQ 9
Kernel modules: i2c_piix4
Before attempting to remove i2c_piix4, lsmod confirmed that it was loaded. To remove it, I edited /etc/modprobe.d/blacklist.conf and added the line blacklist i2c_piix4, then called sudo update-initramfs -u and rebooted. Now, the module has disappeared from lsmod, but is still listed under lspci. This is still true after modprobe -r. Have I properly blacklisted it, or is there another step I need to add?
lspci shows the hardware on the pci bus - no matter if a corresponding kernel module is loaded or not.
To remove a device you can do this in the qemu monitor by id or locate it with info qtree and info qom-tree and remove it with device_del.
But removing your specific device is not supported on the ps-i440fx architecture.
(qemu) info qom-tree /machine/unattached/device[24]
/device[24] (PIIX4_PM)
/piix4-pm[0] (qemu:memory-region)
/acpi-cpu-hotplug[0] (qemu:memory-region)
/acpi-evt[0] (qemu:memory-region)
/acpi-tmr[0] (qemu:memory-region)
/apm-io[0] (qemu:memory-region)
/bus master container[0] (qemu:memory-region)
/bus master[0] (qemu:memory-region)
/acpi-pci-hotplug[0] (qemu:memory-region)
/pm-smbus[0] (qemu:memory-region)
/acpi-gpe0[0] (qemu:memory-region)
/i2c (i2c-bus)
/acpi-cnt[0] (qemu:memory-region)
(qemu)
(qemu) device_del /machine/unattached/device[24]
Device 'PIIX4_PM' does not support hotplugging
(qemu)