Hi,

I have some questions about the hpm CSRs.

• There is a conspicuous lack of an interrupt associated with a counter overflow.  Are custom interrupts expected to be provided in a RISC-V implementation?
• What model does Linux perf assume for the use of the monitors? Does a standard release not use interrupts and if so, is polling used instead?
• An SBI interface would seem to be needed for Supervisor/Linux to set the events? Is there a standard call defined?

This link alludes to similar issues, but it also says RISC-V implementations exist w/o an interrupt capabilty.

https://www.kernel.org/doc/html/latest/riscv/pmu.html

Thanks,

Sanjay