| # Shadow ioeventfd |
| |
| Shadow ioeventfd is mechanism that reduces the cost of MMIO writes in |
| vfio-user. In a nutshell, it eliminates the involvement of the VMM by allowing |
| KVM to write the MMIO value in a piece of memory provided by the device |
| emulation task and then notifying it by kicking the ioeventfd. The device |
| emulation task can then find the value in a known location. |
| |
| This mechanism is especially important for cases where the MMIO value is |
| required by the device protocol, which is the case for NVMe. |
| |
| This functionality requires patching the kernel (KVM) and QEMU: |
| - kernel patches: https://github.com/tmakatos/linux/tree/shadow-ioeventfd |
| - QEMU patches: https://github.com/tmakatos/qemu/tree/shadow-ioeventfd |
| |
