On Wed, 2022-03-23 at 16:35 +1300, Tian, Kevin wrote: > > From: Kai Huang <kai.huang@xxxxxxxxx> > > Sent: Sunday, March 13, 2022 6:50 PM > > > > Secure Arbitration Mode (SEAM) is an extension of VMX architecture. It > > defines a new VMX root operation (SEAM VMX root) and a new VMX non- > > root > > operation (SEAM VMX non-root) which isolate from legacy VMX root and > > VMX > > non-root mode. > > s/isolate/are isolated/ OK thanks. > > > > > A CPU-attested software module (called the 'TDX module') runs in SEAM > > VMX root to manage the crypto protected VMs running in SEAM VMX non- > > root. > > SEAM VMX root is also used to host another CPU-attested software module > > (called the 'P-SEAMLDR') to load and update the TDX module. > > > > Host kernel transits to either the P-SEAMLDR or the TDX module via the > > new SEAMCALL instruction. SEAMCALLs are host-side interface functions > > defined by the P-SEAMLDR and the TDX module around the new SEAMCALL > > instruction. They are similar to a hypercall, except they are made by > > "SEAMCALLs are ... functions ... around the new SEAMCALL instruction" > > This is confusing. Probably just: May I ask why is it confusing? > > "SEAMCALL functions are defined and handled by the P-SEAMLDR and > the TDX module" > > > host kernel to the SEAM software. > > > > SEAMCALLs use an ABI different from the x86-64 system-v ABI. Instead, > > they share the same ABI with the TDCALL. %rax is used to carry both the > > SEAMCALL leaf function number (input) and the completion status code > > (output). Additional GPRs (%rcx, %rdx, %r8->%r11) may be further used > > as both input and output operands in individual leaf SEAMCALLs. > > > > Implement a C function __seamcall() to do SEAMCALL using the assembly > > macro used by __tdx_module_call() (the implementation of TDCALL). The > > only exception not covered here is TDENTER leaf function which takes > > all GPRs and XMM0-XMM15 as both input and output. The caller of TDENTER > > should implement its own logic to call TDENTER directly instead of using > > this function. > > > > SEAMCALL instruction is essentially a VMExit from VMX root to SEAM VMX > > root, and it can fail with VMfailInvalid, for instance, when the SEAM > > software module is not loaded. The C function __seamcall() returns > > TDX_SEAMCALL_VMFAILINVALID, which doesn't conflict with any actual error > > code of SEAMCALLs, to uniquely represent this case. > > SEAMCALL is TDX specific, is it? If yes, there is no need to have both > TDX and SEAMCALL in one macro, i.e. above can be SEAMCALL_VMFAILINVALID. This is defined in TDX guest series. I just use it. https://lore.kernel.org/lkml/20220324152415.grt6xvhblmd4uccu@xxxxxxxxxxxxxxxxxx/T/#md0b1aa563bd003ab625de159612a0d07e3ded7cb -- Thanks, -Kai
