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. """ 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. 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. -- Vitaly
