On Mon, 2023-09-18 at 08:44 -0700, Dave Hansen wrote: > On 9/18/23 05:08, Huang, Kai wrote: > > On Fri, 2023-09-15 at 10:50 -0700, Dave Hansen wrote: > > > On 9/15/23 10:43, Edgecombe, Rick P wrote: > > > > On Sat, 2023-08-26 at 00:14 +1200, Kai Huang wrote: > > > > > There are two problems in terms of using kexec() to boot to a new > > > > > kernel when the old kernel has enabled TDX: 1) Part of the memory > > > > > pages are still TDX private pages; 2) There might be dirty > > > > > cachelines associated with TDX private pages. > > > > Does TDX support hibernate? > > > No. > > > > > > There's a whole bunch of volatile state that's generated inside the CPU > > > and never leaves the CPU, like the ephemeral key that protects TDX > > > module memory. > > > > > > SGX, for instance, never even supported suspend, IIRC. Enclaves just > > > die and have to be rebuilt. > > > > Right. AFAICT TDX cannot survive from S3 either. All TDX keys get lost when > > system enters S3. However I don't think TDX can be rebuilt after resume like > > SGX. Let me confirm with TDX guys on this. > > By "rebuilt" I mean all private data is totally destroyed and rebuilt > from scratch. The SGX architecture provides zero help other than > delivering a fault and saying: "whoops all your data is gone". Right. For TDX I am worrying about SEAMCALL could poison memory thus could trigger #MC inside kernel, or even could trigger #MC inside SEAM, instead of delivering a fault that SGX app/kernel can handle. I am confirming with TDX team. > > > I think we can register syscore_ops->suspend for TDX, and refuse to suspend when > > TDX is enabled. This covers hibernate case too. > > > > In terms of how to check "TDX is enabled", ideally it's better to check whether > > TDX module is actually initialized, but the worst case is we can use > > platform_tdx_enabled(). (I need to think more on this) > > *Ideally* the firmware would have a choke point where it could just tell > the OS that it can't suspend rather than the OS having to figure it out. Agreed. Let me ask TDX team about this too.
