On Wed, Oct 12, 2016 at 12:18:50AM +0200, Torbjörn Granlund wrote:
PS. Does RISC-V have some sort of wait-for-interrupt instruction? I
mean, an instruction suitable for the kernel idle loop which waits for
interrupt, allowing hardware and simulators to save energy. If not, one
should be proposed to the UCB folks.
The current privspec 1.9 (draft):
https://content.riscv.org/wp-content/uploads/2016/07/riscv-privileged-v1....
defines a WFI instruction, literally Wait For Interrupt (section 3.2.2).
However IIRC the reason qemu-system-riscv busy-waits is nothing to do
with this, it's because the interim device model is a big hack. Soon
to be replaced with virtio, we are all hoping.
Rich.
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