On Jun 9, 2013, at 4:23 PM, David Daney wrote: > On 06/09/2013 12:31 AM, Gleb Natapov wrote: >> On Fri, Jun 07, 2013 at 04:15:00PM -0700, David Daney wrote: >>> I should also add that I will shortly send patches for the kvm tool >>> required to drive this VM as well as a small set of patches that >>> create a para-virtualized MIPS/Linux guest kernel. >>> >>> The idea is that because there is no standard SMP linux system, we >>> create a standard para-virtualized system that uses a handful of >>> hypercalls, but mostly just uses virtio devices. It has no emulated >>> real hardware (no 8250 UART, no emulated legacy anything...) >>> >> Virtualization is useful for running legacy code. Why dismiss support >> for non pv guests so easily? > > Just because we create standard PV system devices, doesn't preclude emulating > real hardware. In fact Sanjay Lal's work includes QEMU support for doing > just this for a MIPS malta board. I just wanted a very simple system I could > implement with the kvm tool in a couple of days, so that is what I initially > did. > > The problem is that almost nobody has real malta boards, they are really only > of interest because QEMU implements a virtual malta board. > > Personally, I see the most interesting us cases of MIPS KVM being a > deployment platform for new services, so legacy support is not so important > to me. That doesn't mean that other people wouldn't want some sort of legacy > support. The problem with 'legacy' on MIPS is that there are hundreds of > legacies to choose from (Old SGI and DEC hardware, various network hardware > from many different vendors, etc.). Which would you choose? > >> How different MIPS SMP systems are? > > o Old SGI heavy metal (several different system architectures). > > o Cavium OCTEON SMP SoCs. > > o Broadcom (several flavors) SoCs > > o Loongson > > > Come to think of it, Emulating SGI hardware might be an interesting case. > There may be old IRIX systems and applications that could be running low on > real hardware. Some of those systems take up a whole room and draw a lot of > power. They might run faster and at much lower power consumption on a modern > 48-Way SMP SoC based system. > >> What >> about running non pv UP systems? > > See above. I think this is what Sanjay Lal is doing.
The KVM implementation from MIPS (currently in mainline) supports UP systems in trap and emulate mode. The patch set I posted earlier adding VZ support also supports SMP. We leverage the Malta board emulation in QEMU to offer full non-PV virtualization: UP system: Malta board with a MIPS 24K processor SMP system: Malta board with a 1074K CMP processor cluster with a GIC. When it comes to PV/non-PV support, I see the two implementations as complementary. If people want full legacy system emulation without any kernel modifications, then they can run the full QEMU/KVM stack, while people interested in pure PV solutions can run the lkvm version. Regards Sanjay -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
