diff options
| -rw-r--r-- | arch/x86/coco/tdx/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/coco/tdx/tdcall.S | 191 | ||||
| -rw-r--r-- | arch/x86/coco/tdx/tdx.c | 24 | ||||
| -rw-r--r-- | arch/x86/include/asm/tdx.h | 30 | ||||
| -rw-r--r-- | arch/x86/kernel/asm-offsets.c | 8 |
5 files changed, 254 insertions, 1 deletions
diff --git a/arch/x86/coco/tdx/Makefile b/arch/x86/coco/tdx/Makefile index c929d53ee059..46c55998557d 100644 --- a/arch/x86/coco/tdx/Makefile +++ b/arch/x86/coco/tdx/Makefile @@ -1,3 +1,3 @@ # SPDX-License-Identifier: GPL-2.0 -obj-y += tdx.o +obj-y += tdx.o tdcall.o diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S new file mode 100644 index 000000000000..662479ccf630 --- /dev/null +++ b/arch/x86/coco/tdx/tdcall.S @@ -0,0 +1,191 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <asm/asm-offsets.h> +#include <asm/asm.h> +#include <asm/frame.h> +#include <asm/unwind_hints.h> + +#include <linux/linkage.h> +#include <linux/bits.h> +#include <linux/errno.h> + +#include "../../virt/vmx/tdx/tdxcall.S" + +/* + * Bitmasks of exposed registers (with VMM). + */ +#define TDX_R10 BIT(10) +#define TDX_R11 BIT(11) +#define TDX_R12 BIT(12) +#define TDX_R13 BIT(13) +#define TDX_R14 BIT(14) +#define TDX_R15 BIT(15) + +/* + * These registers are clobbered to hold arguments for each + * TDVMCALL. They are safe to expose to the VMM. + * Each bit in this mask represents a register ID. Bit field + * details can be found in TDX GHCI specification, section + * titled "TDCALL [TDG.VP.VMCALL] leaf". + */ +#define TDVMCALL_EXPOSE_REGS_MASK ( TDX_R10 | TDX_R11 | \ + TDX_R12 | TDX_R13 | \ + TDX_R14 | TDX_R15 ) + +/* + * __tdx_module_call() - Used by TDX guests to request services from + * the TDX module (does not include VMM services) using TDCALL instruction. + * + * Transforms function call register arguments into the TDCALL register ABI. + * After TDCALL operation, TDX module output is saved in @out (if it is + * provided by the user). + * + *------------------------------------------------------------------------- + * TDCALL ABI: + *------------------------------------------------------------------------- + * Input Registers: + * + * RAX - TDCALL Leaf number. + * RCX,RDX,R8-R9 - TDCALL Leaf specific input registers. + * + * Output Registers: + * + * RAX - TDCALL instruction error code. + * RCX,RDX,R8-R11 - TDCALL Leaf specific output registers. + * + *------------------------------------------------------------------------- + * + * __tdx_module_call() function ABI: + * + * @fn (RDI) - TDCALL Leaf ID, 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 status of TDCALL via RAX. + */ +SYM_FUNC_START(__tdx_module_call) + FRAME_BEGIN + TDX_MODULE_CALL host=0 + FRAME_END + ret +SYM_FUNC_END(__tdx_module_call) + +/* + * __tdx_hypercall() - Make hypercalls to a TDX VMM using TDVMCALL leaf + * of TDCALL instruction + * + * Transforms values in function call argument struct tdx_hypercall_args @args + * into the TDCALL register ABI. After TDCALL operation, VMM output is saved + * back in @args. + * + *------------------------------------------------------------------------- + * TD VMCALL ABI: + *------------------------------------------------------------------------- + * + * Input Registers: + * + * RAX - TDCALL instruction leaf number (0 - TDG.VP.VMCALL) + * RCX - BITMAP which controls which part of TD Guest GPR + * is passed as-is to the VMM and back. + * R10 - Set 0 to indicate TDCALL follows standard TDX ABI + * specification. Non zero value indicates vendor + * specific ABI. + * R11 - VMCALL sub function number + * RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific arguments. + * R8-R9, R12-R15 - Same as above. + * + * Output Registers: + * + * RAX - TDCALL instruction status (Not related to hypercall + * output). + * R10 - Hypercall output error code. + * R11-R15 - Hypercall sub function specific output values. + * + *------------------------------------------------------------------------- + * + * __tdx_hypercall() function ABI: + * + * @args (RDI) - struct tdx_hypercall_args for input and output + * @flags (RSI) - TDX_HCALL_* flags + * + * On successful completion, return the hypercall error code. + */ +SYM_FUNC_START(__tdx_hypercall) + FRAME_BEGIN + + /* Save callee-saved GPRs as mandated by the x86_64 ABI */ + push %r15 + push %r14 + push %r13 + push %r12 + + /* Mangle function call ABI into TDCALL ABI: */ + /* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */ + xor %eax, %eax + + /* Copy hypercall registers from arg struct: */ + movq TDX_HYPERCALL_r10(%rdi), %r10 + movq TDX_HYPERCALL_r11(%rdi), %r11 + movq TDX_HYPERCALL_r12(%rdi), %r12 + movq TDX_HYPERCALL_r13(%rdi), %r13 + movq TDX_HYPERCALL_r14(%rdi), %r14 + movq TDX_HYPERCALL_r15(%rdi), %r15 + + movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx + + tdcall + + /* + * RAX==0 indicates a failure of the TDVMCALL mechanism itself and that + * something has gone horribly wrong with the TDX module. + * + * The return status of the hypercall operation is in a separate + * register (in R10). Hypercall errors are a part of normal operation + * and are handled by callers. + */ + testq %rax, %rax + jne .Lpanic + + /* TDVMCALL leaf return code is in R10 */ + movq %r10, %rax + + /* Copy hypercall result registers to arg struct if needed */ + testq $TDX_HCALL_HAS_OUTPUT, %rsi + jz .Lout + + movq %r10, TDX_HYPERCALL_r10(%rdi) + movq %r11, TDX_HYPERCALL_r11(%rdi) + movq %r12, TDX_HYPERCALL_r12(%rdi) + movq %r13, TDX_HYPERCALL_r13(%rdi) + movq %r14, TDX_HYPERCALL_r14(%rdi) + movq %r15, TDX_HYPERCALL_r15(%rdi) +.Lout: + /* + * Zero out registers exposed to the VMM to avoid speculative execution + * with VMM-controlled values. This needs to include all registers + * present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15 + * context will be restored. + */ + xor %r10d, %r10d + xor %r11d, %r11d + + /* Restore callee-saved GPRs as mandated by the x86_64 ABI */ + pop %r12 + pop %r13 + pop %r14 + pop %r15 + + FRAME_END + + retq +.Lpanic: + call __tdx_hypercall_failed + /* __tdx_hypercall_failed never returns */ + jmp .Lpanic +SYM_FUNC_END(__tdx_hypercall) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 97674471fd1e..4b57880e45b0 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -7,6 +7,30 @@ #include <linux/cpufeature.h> #include <asm/tdx.h> +/* + * Wrapper for standard use of __tdx_hypercall with no output aside from + * return code. + */ +static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15) +{ + struct tdx_hypercall_args args = { + .r10 = TDX_HYPERCALL_STANDARD, + .r11 = fn, + .r12 = r12, + .r13 = r13, + .r14 = r14, + .r15 = r15, + }; + + return __tdx_hypercall(&args, 0); +} + +/* Called from __tdx_hypercall() for unrecoverable failure */ +void __tdx_hypercall_failed(void) +{ + panic("TDVMCALL failed. TDX module bug?"); +} + void __init tdx_early_init(void) { u32 eax, sig[3]; diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index cb4c4e607c43..a33d47abe67d 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -3,12 +3,17 @@ #ifndef _ASM_X86_TDX_H #define _ASM_X86_TDX_H +#include <linux/bits.h> #include <linux/init.h> #include <linux/bits.h> #define TDX_CPUID_LEAF_ID 0x21 #define TDX_IDENT "IntelTDX " +#define TDX_HYPERCALL_STANDARD 0 + +#define TDX_HCALL_HAS_OUTPUT BIT(0) + /* * SW-defined error codes. * @@ -36,10 +41,35 @@ struct tdx_module_output { u64 r11; }; +/* + * Used in __tdx_hypercall() to pass down and get back registers' values of + * the TDCALL instruction when requesting services from the VMM. + * + * This is a software only structure and not part of the TDX module/VMM ABI. + */ +struct tdx_hypercall_args { + u64 r10; + u64 r11; + u64 r12; + u64 r13; + u64 r14; + u64 r15; +}; + #ifdef CONFIG_INTEL_TDX_GUEST void __init tdx_early_init(void); +/* Used to communicate with the TDX module */ +u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9, + struct tdx_module_output *out); + +/* Used to request services from the VMM */ +u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags); + +/* Called from __tdx_hypercall() for unrecoverable failure */ +void __tdx_hypercall_failed(void); + #else static inline void tdx_early_init(void) { }; diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c index 7dca52f5cfc6..437308004ef2 100644 --- a/arch/x86/kernel/asm-offsets.c +++ b/arch/x86/kernel/asm-offsets.c @@ -75,6 +75,14 @@ static void __used common(void) OFFSET(TDX_MODULE_r11, tdx_module_output, r11); BLANK(); + OFFSET(TDX_HYPERCALL_r10, tdx_hypercall_args, r10); + OFFSET(TDX_HYPERCALL_r11, tdx_hypercall_args, r11); + OFFSET(TDX_HYPERCALL_r12, tdx_hypercall_args, r12); + OFFSET(TDX_HYPERCALL_r13, tdx_hypercall_args, r13); + OFFSET(TDX_HYPERCALL_r14, tdx_hypercall_args, r14); + OFFSET(TDX_HYPERCALL_r15, tdx_hypercall_args, r15); + + BLANK(); OFFSET(BP_scratch, boot_params, scratch); OFFSET(BP_secure_boot, boot_params, secure_boot); OFFSET(BP_loadflags, boot_params, hdr.loadflags); |