Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes: > Changes since v2: > - Renamed 'msr_bitmap_changed' to 'msr_bitmap_force_recalc' [Paolo] and > expanded the comment near its definition explaining its limited > usefulness [Sean]. > > Original description: > > Updating MSR bitmap for L2 is not cheap and rearly needed. TLFS for Hyper-V > offers 'Enlightened MSR Bitmap' feature which allows L1 hypervisor to > inform L0 when it changes MSR bitmap, this eliminates the need to examine > L1's MSR bitmap for L2 every time when 'real' MSR bitmap for L2 gets > constructed. > > When the feature is enabled for Win10+WSL2, it shaves off around 700 CPU > cycles from a nested vmexit cost (tight cpuid loop test). > > First patch of the series is unrelated to the newly implemented feature, > it fixes a bug in Enlightened MSR Bitmap usage when KVM runs as a nested > hypervisor on top of Hyper-V. > Ping? -- Vitaly
