On Thu, 2021-05-06 at 10:16 -0700, Jim Mattson wrote: > On Thu, May 6, 2021 at 3:34 AM <ilstam@xxxxxxxxxxx> wrote: > > > > From: Ilias Stamatis <ilstam@xxxxxxxxxx> > > > > KVM currently supports hardware-assisted TSC scaling but only for L1 > > and it > > doesn't expose the feature to nested guests. This patch series adds > > support for > > nested TSC scaling and allows both L1 and L2 to be scaled with > > different > > scaling factors. > > > > When scaling and offsetting is applied, the TSC for the guest is > > calculated as: > > > > (TSC * multiplier >> 48) + offset > > > > With nested scaling the values in VMCS01 and VMCS12 need to be > > merged > > together and stored in VMCS02. > > > > The VMCS02 values are calculated as follows: > > > > offset_02 = ((offset_01 * mult_12) >> 48) + offset_12 > > mult_02 = (mult_01 * mult_12) >> 48 > > > > The last patch of the series adds a KVM selftest. > > Will you be doing the same for SVM? The last time I tried to add a > nested virtualization feature for Intel only, Paolo rapped my knuckles > with a ruler. Yes, I can try do this, if it's not much more complicated, once I get access to AMD hardware. But I suppose this series is standalone and could be merged separately? By taking a quick look it seems that SVM exposes far less features to nested guests than VMX does anyway. Ilias
