> From: Dave Hansen <dave.hansen@xxxxxxxxx> > Sent: Monday, November 21, 2022 12:39 PM > [...] > On 11/21/22 11:51, Dexuan Cui wrote: > > __tdx_hypercall() doesn't work for a TDX guest running on Hyper-V, > > because Hyper-V uses a different calling convention, so add the > > new function __tdx_ms_hv_hypercall(). > > Other than R10 being variable here and fixed for __tdx_hypercall(), this > looks *EXACTLY* the same as __tdx_hypercall(), or at least a strict > subset of what __tdx_hypercall() can do. > > Did I miss something? The existing asm code for __tdx_hypercall() passes through R10~R15 (see TDVMCALL_EXPOSE_REGS_MASK) to the (KVM) hypervisor. Unluckily, for Hyper-V, we need to pass through RDX, R8, R10 and R11 to Hyper-V, so I don't think I can use the existing __tdx_hypercall() ? > Another way of saying this: It seems like you could do this with a new > version of _tdx_hypercall() (and all in C) instead of a new > __tdx_hypercall(). I don't think the current TDVMCALL_EXPOSE_REGS_MASK allows me to pass through RDX and R8 to Hyper-V. PS, the comment before __tdx_hypercall() contains this line: "* RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific arguments." But it looks like currently RBX an RBP are not used at all in arch/x86/coco/tdx/tdcall.S ?
