On 6/7/23 11:53, Isaku Yamahata wrote: >>> VMX enabling, and KVM is the only user of TDX. This implementation >>> chooses to make KVM itself responsible for enabling VMX before using >>> TDX and let the rest of the kernel stay blissfully unaware of VMX. >>> >>> The current TDX_MODULE_CALL macro handles neither #GP nor #UD. The >>> kernel would hit Oops if SEAMCALL were mistakenly made w/o enabling VMX >>> first. Architecturally, there is no CPU flag to check whether the CPU >>> is in VMX operation. Also, if a BIOS were buggy, it could still report >>> valid TDX private KeyIDs when TDX actually couldn't be enabled. >> I'm not sure this is a great justification. If the BIOS is lying to the >> OS, we _should_ oops. >> >> How else can this happen other than silly kernel bugs. It's OK to oops >> in the face of silly kernel bugs. > TDX KVM + reboot can hit #UD. On reboot, VMX is disabled (VMXOFF) via > syscore.shutdown callback. However, guest TD can be still running to issue > SEAMCALL resulting in #UD. > > Or we can postpone the change and make the TDX KVM patch series carry a patch > for it. How does the existing KVM use of VMLAUNCH/VMRESUME avoid that problem?
