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e8296dce05
This patch introduce a new mode of IO request completion, polling mode.
Now, the sketch of ioreq process can be,
A. UOS vcpu0 generate PIO/MMIO ->
B. pcpu1(vcpu0 of UOS) trap into HV ->
C. pcpu1 build ioreq, send IPI and enter idle ->
D.1 pcpu0(vcpu0 of SOS) response IPI,
D.2 pcpu0 handle the ioreq in HV, kernel, DM,
D.3 pcpu0 mark ioreq as complete,
D.4 pcpu0 hypercall to enter HV ->
E.1 pcpu0 send IPI to wake pcpu1 up
E.2 UOS vcpu0 continue running
With this change, it skips D.4, E.1 steps. In step C, pcpu1 will enter a
polling ioreq state idle after send out the IPI.
It can save about ~5000 cpu cycles.
In polling mode, we do the polling in idle instead of pause cpu all the
time. It will consume more power. A better way is to use monitor/mwait
instructions which can put cpu into a sleep state with monitoring a
memory address. Unfortunately, APL has bug with monitor. We can gather
all ioreqs state into one monitorable memory and take advantage of
monitor/mwait for future platform.
The way polling or notification is per VM. We can config VMs in
different mode. By default, IO request completion will use notification
mode for all VMs. We can switch it by Kconfig.
Tracked-On: #1821
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Reviewed-by: Eddie Dong <eddie.dong@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>
ACRN Hypervisor ############### The open source `Project ACRN`_ defines a device hypervisor reference stack and an architecture for running multiple software subsystems, managed securely, on a consolidated system by means of a virtual machine manager. It also defines a reference framework implementation for virtual device emulation, called the “ACRN Device Model”. The ACRN Hypervisor is a Type 1 reference hypervisor stack, running directly on the bare-metal hardware, and is suitable for a variety of IoT and embedded device solutions. The ACRN hypervisor addresses the gap that currently exists between datacenter hypervisors, and hard partitioning hypervisors. The ACRN hypervisor architecture partitions the system into different functional domains, with carefully selected guest OS sharing optimizations for IoT and embedded devices. You can find out more about Project ACRN on the `Project ACRN documentation`_ website. .. _`Project ACRN`: https://projectacrn.org .. _`ACRN Hypervisor`: https://github.com/projectacrn/acrn-hypervisor .. _`Project ACRN documentation`: https://projectacrn.github.io/