From: MUKESH RATHOR <mukeshrathor@xxxxxxxxxxxxx> Sent: Monday, November 11, 2024 3:11 PM > > On 11/11/24 13:28, Michael Kelley wrote: > > From: MUKESH RATHOR <mukeshrathor@xxxxxxxxxxxxx> Sent: Monday, November 11, 2024 10:53 AM > >> > >> On 11/10/24 20:12, Michael Kelley wrote: > >> > From: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> Sent: > >> Thursday, November 7, 2024 2:32 PM > >> >> > >> >> To support Hyper-V Dom0 (aka Linux as root partition), many new > >> >> definitions are required. > >> > > >> > Using "dom0" terminology here and in the Subject: line is likely to > >> > be confusing to folks who aren't intimately involved in Hyper-V work. > >> > Previous Linux kernel commit messages and code for running in the > >> > Hyper-V root partition use "root partition" terminology, and I couldn't > >> > find "dom0" having been used before. "root partition" would be more > >> > consistent, and it also matches the public documentation for Hyper-V. > >> > "dom0" is Xen specific terminology, and having it show up in Hyper-V > >> > patches would be confusing for the casual reader. I know "dom0" has > >> > been used internally at Microsoft as shorthand for "Hyper-V root > >> > partition", but it's probably best to completely avoid such shorthand > >> > in public Linux kernel patches and code. > >> > > >> > Just my $.02 .... > >> > >> Hi Michael, > >> > >> FWIW, hyperv team and us are using the term "dom0" more and more to > >> avoid confusion between windows root and linux root, as dom0 is > >> always linux root. I did a quick search, and "dom0" is neither > >> copyrighted nor trademarked by xen, and I'm sure the fine folks > >> there won't be offended. Hopefully, [Hyper-V] tag would reduce > >> the confusion. > >> > >> Just my $0.1 > >> > > > > Yeah, "dom0" certainly fits as shorthand for the rather ponderous > > "Linux running in a Hyper-V root partition". :-) > > > > But even using "Hyper-V dom0" to add clarity vs. Xen dom0 seems > > to me to be a misnomer because Hyper-V dom0 is only conceptually > > like Xen dom0. It's not actually an implementation of Xen dom0. > > Let me give two examples: > > > > 1) Hyper-V provides VMBus, which is conceptually similar to virtio. > > But VMBus is not an implementation of virtio, and we don't call it > > "Hyper-V virtio". Of course, "VMBus" is a lot shorter than "Hyper-V > > root partition" so the motivation for a shorthand isn't there, but still. > > If Hyper-V should ever implement actual virtio interfaces, then it > > would be valid to call that "Hyper-V virtio". > > > > 2) KVM has "KVM Hyper-V", which I think is valid. It's an > > implementation of Hyper-V interfaces in KVM so that Windows > > guests can run as if they are running on Hyper-V. > > > > I won't speculate on what the Xen folks would think of "Hyper-V > > dom0", especially if it isn't an implementation that's compatible > > with Xen dom0 functionality. > > > > As for "more and more" usage of "dom0" by your team and the > > Hyper-V team: Is that internal usage only? Or usage in public mailing > > lists or open source projects like Cloud Hypervisor? Again, from > > my standpoint, internal is internal and can be whatever is convenient > > and properly understood internally. But in public mailing lists and > > projects, I think "Hyper-V dom0" should be avoided unless it's > > truly an implementation of the dom0 interfaces. > > > > That's probably now $0.10 worth instead of $0.02. :-) And I'm > > not the decider here -- I'm just offering a perspective. > > "dom0" is neither a technology nor a protocol. It simply means initial > domain (which on xen happened to be domid of 0, could have been 1). This > is created during boot, same as linux root on hyperv, and is privileged > domain same as xen. Even in KVM world, I've heard many folks refer to > the host as kvm dom0... > > Given the mix of windows and linux with l1vh and nested, dom0 is helping > in conversations internally, and I'm sure it will keep percolating > externally. > OK, fair enough. My perspective is probably more limited than yours as my experience with "dom0" is exclusively with the Xen code in a Linux kernel environment. I just haven't seen "dom0" used elsewhere, but that certainly doesn't mean it's not being done. If the decision on the Microsoft side is that introducing "Hyper-V dom0" terminology makes sense, I won't object further, though I would think there should be some kind of reconciliation with existing code/comments/documentation that uses "root partition". Michael
