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. A CPU-attested software module (called 'TDX module') runs in SEAM VMX root to manage the protected VMs running in SEAM VMX non-root. SEAM VMX root is also used to host another CPU-attested software module (called 'P-SEAMLDR') to load and update the TDX module. Host kernel transits to either P-SEAMLDR or TDX module via the new SEAMCALL instruction. SEAMCALLs are host-side interface functions defined by P-SEAMLDR and TDX module around the new SEAMCALL instruction. They are similar to a hypercall, except they are made by host kernel to the SEAM software. SEAMCALLs use an ABI different from the x86-64 system-v ABI. Instead, it shares 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. It fails with VMfailInvalid when the SEAM software 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. Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx> --- arch/x86/virt/vmx/Makefile | 2 +- arch/x86/virt/vmx/seamcall.S | 53 ++++++++++++++++++++++++++++++++++++ arch/x86/virt/vmx/tdx.h | 11 ++++++++ 3 files changed, 65 insertions(+), 1 deletion(-) create mode 100644 arch/x86/virt/vmx/seamcall.S create mode 100644 arch/x86/virt/vmx/tdx.h diff --git a/arch/x86/virt/vmx/Makefile b/arch/x86/virt/vmx/Makefile index 1bd688684716..fd577619620e 100644 --- a/arch/x86/virt/vmx/Makefile +++ b/arch/x86/virt/vmx/Makefile @@ -1,2 +1,2 @@ # SPDX-License-Identifier: GPL-2.0-only -obj-$(CONFIG_INTEL_TDX_HOST) += tdx.o +obj-$(CONFIG_INTEL_TDX_HOST) += tdx.o seamcall.o diff --git a/arch/x86/virt/vmx/seamcall.S b/arch/x86/virt/vmx/seamcall.S new file mode 100644 index 000000000000..65edec23b5f4 --- /dev/null +++ b/arch/x86/virt/vmx/seamcall.S @@ -0,0 +1,53 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <linux/linkage.h> +#include <asm/frame.h> + +#include "../tdxcall.S" + +/* + * __seamcall() - Host-side interface functions to SEAM software + * (P-SEAMLDR or TDX module) + * + * Transform function call register arguments into the SEAMCALL register + * ABI. Return TDX_SEAMCALL_VMFAILINVALID (when SEAM software is not + * loaded or SEAMCALLs are made into P-SEAMLDR concurrently), or the + * completion status of the SEAMCALL. Additional output operands are + * saved in @out (if it is provided by the user). + * + *------------------------------------------------------------------------- + * SEAMCALL ABI: + *------------------------------------------------------------------------- + * Input Registers: + * + * RAX - SEAMCALL Leaf number. + * RCX,RDX,R8-R9 - SEAMCALL Leaf specific input registers. + * + * Output Registers: + * + * RAX - SEAMCALL completion status code. + * RCX,RDX,R8-R11 - SEAMCALL Leaf specific output registers. + * + *------------------------------------------------------------------------- + * + * __seamcall() function ABI: + * + * @fn (RDI) - SEAMCALL Leaf number, moved to RAX + * @rcx (RSI) - Input parameter 1, moved to RCX + * @rdx (RDX) - Input parameter 2, moved to RDX + * @r8 (RCX) - Input parameter 3, moved to R8 + * @r9 (R8) - Input parameter 4, moved to R9 + * + * @out (R9) - struct tdx_module_output pointer + * stored temporarily in R12 (not + * shared with the TDX module). It + * can be NULL. + * + * Return (via RAX) the completion status of the SEAMCALL, or + * TDX_SEAMCALL_VMFAILINVALID. + */ +SYM_FUNC_START(__seamcall) + FRAME_BEGIN + TDX_MODULE_CALL host=1 + FRAME_END + ret +SYM_FUNC_END(__seamcall) diff --git a/arch/x86/virt/vmx/tdx.h b/arch/x86/virt/vmx/tdx.h new file mode 100644 index 000000000000..9d5b6f554c20 --- /dev/null +++ b/arch/x86/virt/vmx/tdx.h @@ -0,0 +1,11 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _X86_VIRT_TDX_H +#define _X86_VIRT_TDX_H + +#include <linux/types.h> + +struct tdx_module_output; +u64 __seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9, + struct tdx_module_output *out); + +#endif -- 2.33.1
