On Fri, 2023-06-30 at 12:21 +0200, Peter Zijlstra wrote: > On Fri, Jun 30, 2023 at 12:07:00PM +0200, Peter Zijlstra wrote: > > On Thu, Jun 29, 2023 at 10:33:38AM +0000, Huang, Kai wrote: > > > > Looking at the later versions of TDX spec (with TD live migration, etc), it > > > seems they are already using R12-R13 as SEAMCALL output: > > > > > > https://cdrdv2.intel.com/v1/dl/getContent/733579 > > > > Urgh.. I think I read an older versio because I got bleeding eyes from > > all this colour coded crap. > > > > All this red is unreadable :-( Have they been told about the glories of > > TeX and diff ? > > > > > E.g., 6.3.15. NEW: TDH.IMPORT.MEM Leaf > > > > > > It uses R12 and R13 as input. > > > > 12 and 14. They skipped 13 for some mysterious raisin. > > Things like TDH.SERVTD.BIND do use R13. > > > But also, 10,11 are frequently used as input with this new stuff, which > > already suggests the setup from your patches is not tenable. > > > TDG.SERVTD.RD *why* can't they pass that TD_UUID as a pointer? Using *4* > registers like that is quite insane. I can ask TDX module team whether they can change to use a buffer instead of 4 registers. > > TDG.VP.ENTER :-(((( that has b,15,si,di as additional output. > > That means there's not a single register left unused. Can we still get > this changed, please?!? > I assume it's TDH.VP.ENTER. TDH.VP.ENTER is a special SEAMCALL because it goes into TDX guest to run. KVM should be the only place that handles it. And KVM won't use the __seamcall() here to handle it but will have it's own assembly. For normal VMX guests, since most GPRs are not saved/restored by hardware, KVM already has sufficient code to save/restore relevant GPRs during VMENTER/VMEXIT. Handling TDX can just follow that pattern. So looks fine to me.
