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
> 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.
>> 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
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.