[Qemu-devel] Re: POLL: Why do you use kqemu?

[Jan Kiszka <jan.kiszka@web.de>]

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Blue Swirl wrote:
> On 6/6/09, Jan Kiszka <jan.kiszka@web.de> wrote:
>> Blue Swirl wrote:
>>  > On 6/6/09, Avi Kivity <avi@redhat.com> wrote:
>>  >> Andreas Färber wrote:
>>  >>
>>  >>> Or as another example, I've been unable to try KVM with svn/git QEMU
>>  >> because new capability defines keep being added that block compiling QEMU
>>  >> with KVM from any mainstream distribution. With nobody here being able to
>>  >> recommend a working distribution, that makes KVM a moot alternative,
>>  >> especially on systems you can't install your own kernel modules on. I just
>>  >> hope that Fedora 11 will let me try it.
>>  >>  Try qemu-kvm.git, that should compile and run on almost anything (and is a
>>  >> lot faster and more featureful than kvm support in qemu.git).
>>  >
>>  > Maybe the backwards compatibility features should be ported to QEMU?
>>  > For example, is there a workaround for
>>  > #error Missing KVM capability KVM_CAP_DESTROY_MEMORY_REGION_WORKS
>>  > ?
>>
>>
>> Given that we have always-up-to-date kvm-kmod packages with support down
>>  to reasonable kernel versions, I would prefer to keep upstream clean
>>  from old workarounds. They should only be needed for issues found very
>>  recently (KVM_CAP_JOIN_MEMORY_REGIONS_WORKS) or that might be found in
>>  the future.
> 
> But then I (and from Andreas' message I gather that many others) can't
> test KVM support on QEMU without building, installing and maintaining
> (updating, rebuilding, reinstalling etc) my own kernel instead of the
> distro build.

You don't have to, it builds against the distro kernel's devel package
(I'm doing most KVM development on boring distro kernels). No black
magic involved. Really.

> 
> Does this also mean that KVM stuff in QEMU releases will not be usable
> for anyone (except those building their own kernels) until distros
> upgrade to a compatible kernel version a few years later?

In a year from now, you won't need any of todays workarounds on a then
up-to-date distro kernel. And given that not only bug fixes come with
kvm-kmod but also feature enhancements, updating the in-kernel kvm
modules that way will likely remain a valid use case even after that point.

Jan


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