On Mon, Oct 16, 2023, Vitaly Kuznetsov wrote: > Sean Christopherson <seanjc@xxxxxxxxxx> writes: > > > On Mon, Oct 16, 2023, Vitaly Kuznetsov wrote: > >> Maxim Levitsky <mlevitsk@xxxxxxxxxx> writes: > >> > > ... > > >> > > >> > "Provides KVM support for emulating Microsoft Hypervisor (Hyper-V). > > > > I don't think we should put Hyper-V in parentheses, I haven't seen any documentation > > that calls it "Microsoft Hypervisor", i.e. Hyper-V is the full and > > proper name. > > Ha :-) From > https://lore.kernel.org/linux-hyperv/1696010501-24584-1-git-send-email-nunodasneves@xxxxxxxxxxxxxxxxxxx/ > > """ > This series introduces support for creating and running guest machines > while running on the Microsoft Hypervisor. [0] > ... > [0] "Hyper-V" is more well-known, but it really refers to the whole stack > including the hypervisor and other components that run in Windows > kernel and userspace. > """ LOL indeed. :-) > I'm fine with keeping the staus quo though :-) > > > > >> > This makes KVM expose a set of paravirtualized interfaces, > > > > s/makes/allows, since KVM still requires userspace to opt-in to exposing Hyper-V. > > > >> > documented in the HyperV TLFS, > > > > s/TLFS/spec? Readers that aren't already familiar with Hyper-V will have no idea > > what TLFS is until they click the link. > > > >> > https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs, > >> > which consists of a subset of paravirtualized interfaces that HyperV exposes > > > > We can trim this paragraph by stating that KVM only supports a subset of the > > PV interfaces straightaway. > > > >> > to its guests. > > > > E.g. > > > > Provides KVM support for for emulating Microsoft Hyper-V. This allows KVM to > > expose a subset of the paravirtualized interfaces defined in Hyper-V's spec: > > https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs. To fold in the whole "Microsoft Hypervisor" thing, what if we take the verbiage verbatim from the TLFS intro? Provides KVM support for emulating Microsoft Hyper-V. This allows KVM to expose a subset of the paravirtualized interfaces defined in the Hyper-V Hypervisor Top-Level Functional Specification (TLFS): https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs > LGTM, thanks! > > > > >> > > >> > This improves performance of modern Windows guests. > > > > Isn't Hyper-V emulation effectively mandatory these days? IIRC, modern versions > > of Windows will fail to boot if they detect a hypervisor but the core Hyper-V > > interfaces aren't supported. > > > > It's rather a rule of thumb: normally, modern Windows and Hyper-V > versions (Win10/11, WS2019/22) boot and pretend to work but without > Hyper-V enlightenment it's not uncommon to see a blue screen of death > because of a watchdog firing. It's hard to say for sure as things keep > changing under the hood so even different builds can behave differently; > pretending we're a genuine Hyper-V was proven to be the most robust > approach. We should capture something to that effect in the help. I want to avoid bug reports of Windows not working on KVM because someone turned off CONFIG_KVM_HYPERV because the help implies that it _only_ improves performance.
