On 30/07/19 15:50, Anup Patel wrote: >> BTW, since IPIs are handled in the SBI I wouldn't bother with in-kernel >> PLIC emulation unless you can demonstrate performance improvements (for >> example due to irqfd). In fact, it may be more interesting to add > > I thought VHOST requires irqfd and we would certainly endup providing > in-kernel PLIC emulation to support VHOST. vhost only needs an eventfd, userspace can poll the eventfd and inject the irq as usual with KVM_INTERRUPT. Of course that can be slower, but you can benchmark it and see if it's indeed a good reason for in-kernel PLIC. >> plumbing for userspace handling of selected SBI calls (in addition to >> get/putchar, sbi_system_reset and sbi_hart_down look like good >> candidates in SBI v0.2). > > The get/putchar SBI v0.1 calls won't be encouraged going forward because > we already have earlycon implmentation in-place and Guest kernel can directly > write to UART registers for earlyprints. > If we still wanted to implement get/putchar calls then we would need a RISC-V > specific exit reason in KVM. We have tried to avoid RISC-V specific IOCTLs > or exit reason in this series. Sounds good. Paolo >> >>> We were thinking to keep KVM RISC-V disabled by default (i.e. keep it >>> experimental) until we have validated it on some FPGA or real HW. For now, >>> users can explicitly enable it and play-around on QEMU emulation. I hope >>> this is fine with most people ? >> >> That's certainly okay with me. >> > > Thanks, > Anup >
