On Thu, Dec 14, 2023, Maxim Levitsky wrote: > On Wed, 2023-12-13 at 15:10 -0800, Sean Christopherson wrote: > > Upstream KVM's non-TDX behavior is fine, because KVM doesn't advertise support > > for CPUID 0x15, i.e. doesn't announce to host userspace that it's safe to expose > > CPUID 0x15 to the guest. Because TDX makes exposing CPUID 0x15 mandatory, KVM > > needs to be taught to correctly emulate the guest's APIC bus frequency, a.k.a. > > the TDX guest core crystal frequency of 25Mhz. > > I assume that TDX doesn't allow to change the CPUID 0x15 leaf. Correct. I meant to call that out below, but left my sentence half-finished. It was supposed to say: I halfheartedly floated the idea of "fixing" the TDX module/architecture to either use 1Ghz as the base frequency or to allow configuring the base frequency advertised to the guest. > > I halfheartedly floated the idea of "fixing" the TDX module/architecture to either > > use 1Ghz as the base frequency (off list), but it definitely isn't a hill worth > > dying on since the KVM changes are relatively simple. > > > > https://lore.kernel.org/all/ZSnIKQ4bUavAtBz6@xxxxxxxxxx > > > > Best regards, > Maxim Levitsky >
