On 02/22/2016 04:14 PM, Peter Maydell wrote: > On 22 February 2016 at 21:06, Wei Huang <w...@redhat.com> wrote: >> We start to see more features been added to ARM virtual machine models. >> For the purpose of backward compatibility (e.g. migration), it is time >> to consider versioning machine types for ARM VMs. As a beginning step, this >> patchset defines an abstract machine type for ARM VMs. The current >> "virt" machine is re-written based on this new machine type accordingly. >> These patches have been verified by booting existing VMs. >> >> Note that I am seeking inputs from the community by putting RFC in the >> subject line. Please let me know your opinions. I will send out V1 >> afterwards. > > My view here is the same as it has been in the past regarding > adding versioned machine types for 'virt': are you (in this case > Redhat) willing to stand behind it, in the sense of taking on > the maintenance burden of adding new machine versions, reviewing > new code contributions for issues that require changes to make sure > that the old versions stay looking like the old machine, testing > that old versions look right, testing cross version migration, > and so on?
I understand your concerns. Currently our in-house tree already carries versioned ARM machine types, which mirror both QEMU 2.4 and QEMU 2.5. Thus someone (including myself) from Red Hat shouldn't have any problem of maintaining/testing it because we are already doing it downstream. x86 and ppc have a similar situation. > > We need versioned machine types at *some* point; my intent here > is to provide sufficient pushback to ensure that we don't give > ourselves the maintenance headache until we truly need it... > mach-virt based products are coming soon, so versioning is just around the corner. The advantage of introducing it upstream early is that the upper layers in the stack have a chance to integrate, and the QEMU downstreams don't need to diverge in how they add versioning support themselves. This benefits not only Red Hat but also other companies. Thanks, -Wei > thanks > -- PMM >
