On Mon, Mar 25, 2024 at 11:14:21AM +0000, "Huang, Kai" <kai.huang@xxxxxxxxx> wrote: > On Fri, 2024-03-22 at 16:06 +0000, Edgecombe, Rick P wrote: > > On Fri, 2024-03-22 at 07:10 +0000, Huang, Kai wrote: > > > > I see that this was suggested by Sean, but can you explain the > > > > problem > > > > that this is working around? From the linked thread, it seems like > > > > the > > > > problem is what to do when userspace also calls SET_CPUID after > > > > already > > > > configuring CPUID to the TDX module in the special way. The choices > > > > discussed included: > > > > 1. Reject the call > > > > 2. Check the consistency between the first CPUID configuration and > > > > the > > > > second one. > > > > > > > > 1 is a lot simpler, but the reasoning for 2 is because "some KVM > > > > code > > > > paths rely on guest CPUID configuration" it seems. Is this a > > > > hypothetical or real issue? Which code paths are problematic for > > > > TDX/SNP? > > > > > > There might be use case that TDX guest wants to use some CPUID which > > > isn't handled by the TDX module but purely by KVM. These (PV) CPUIDs > > > need to be > > > provided via KVM_SET_CPUID2. > > > > Right, but are there any needed today? > > > > I am not sure. Isaku may know better? It's not needed to boot TD. The check is safe guard. The multiple of source of cpuids can be inconsistent. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
