This patch series adds support for user space save/restore of the VGIC state. Instead of expanding the ONE_REG interface, which works on VCPUs, we first introduce support for the new KVM device control API and the VGIC. Now, instead of calling KVM_CREATE_IRQCHIP, user space can call KVM_CREATE_DEVICE and perform operations on the device fd, such as KVM_SET_DEVICE_ATTR to set a device attribute.
We leverage the KVM_{SET/GET}_DEVICE_ATTR API to export the state of the VGIC to user space. Instead of coming up with our own custom format for exporting the VGIC state, we simply export all the state visible to an emulated guest, which must contain the full GIC state to provide save/restore of the GIC state for power management purposes. This further provides the benefit of being able to re-use the MMIO emulation code for the distributor for save/restore.
However, the need to save/restore cpu-specific state demands that user space can save/restore state accessible through the CPU interface, and we therefore add an emulation interface for the CPU-specific interface.
This is considered a first attempt, and I am not married to the device control API. If there are good technical arguments to take another approach, I am of course willing to discuss this. However, my attempts with the ONE_REG interface did not look very nice.
[ WARINING: The patch set core functionality is completely untested; the basic KVM system has been briefly tested on TC2 and it doesn't seem like I've broken existing functionality. ]
I wanted to get this out early to get feedback on the overall API and idea, and I'm writing some user QEMU for the user space side to test the new functionality meanwhile.
Patches are against kvm-arm-next and also available here: git://git.linaro.org/people/cdall/linux-kvm-arm.git vgic-migrate
Christoffer Dall (7): KVM: arm-vgic: Support KVM_CREATE_DEVICE for VGIC KVM: arm-vgic: Set base addr through device API irqchip: arm-gic: Define additional MMIO offsets and masks KVM: arm-vgic: Make vgic mmio functions more generic KVM: arm-vgic: Add vgic reg access from dev attr KVM: arm-vgic: Add GICD_SPENDSGIR and GICD_CPENDSGIR handlers KVM: arm-vgic: Support CPU interface reg access
Documentation/virtual/kvm/api.txt | 5 +- Documentation/virtual/kvm/devices/arm-vgic.txt | 52 +++ arch/arm/include/uapi/asm/kvm.h | 8 + arch/arm/kvm/arm.c | 3 +- include/kvm/arm_vgic.h | 2 +- include/linux/irqchip/arm-gic.h | 14 + include/linux/kvm_host.h | 1 + include/uapi/linux/kvm.h | 1 + virt/kvm/arm/vgic.c | 452 +++++++++++++++++++++++- virt/kvm/kvm_main.c | 4 + 10 files changed, 522 insertions(+), 20 deletions(-) create mode 100644 Documentation/virtual/kvm/devices/arm-vgic.txt