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

[Blue Swirl <blauwirbel@gmail.com>]

On 6/7/09, Jan Kiszka <jan.kiszka@web.de> wrote:
> Avi Kivity wrote:
>  > Jan Kiszka wrote:
>  >>> 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.
>  >>
>  >
>  > Requiring the latest up-to-date modules is pushing the problem to the
>  > users.  Sometimes there is no choice, but when there is, the
>  > implementation that cares about its uses prefer unclean code and
>  > functionality over perfection and brokenness.
>
>
> Let's make it more concrete:
>
>  By the time upstream is as well tested, feature-rich and with comparable
>  performance as qemu-kvm, its current baseline requirement (2.6.29 due to
>  KVM_CAP_DESTROY_MEMORY_REGION_WORKS) will no longer be a problem to most
>  normal users. Until then they are better off with qemu-kvm anyway.
>
>  So all I wanted to express is that I see no point in merging workarounds
>  upstream that hardly anyone will need but that restrict non-kvm code in
>  upstream. Basically I have the current line along
>  KVM_CAP_DESTROY_MEMORY_REGION_WORKS / clean memory slot management in
>  mind. Anything older should be skipped when merging upstream. And unless
>  something more problematic comes along (rather unlikely), 2.6.29 or
>  compatible kvm-kmod is a reasonable minimum requirement for the long term.

I pulled qemu-kvm and it looks to me that
KVM_CAP_DESTROY_MEMORY_REGION_WORKS and the derived functions
kvm_destroy_memory_region_works() and must_use_aliases_*() are only
used in very few places. Do I miss something, how can this be of any
restriction?