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- /* 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
- /*
- * For the idle loop STI needs to be called directly before the TDCALL
- * that enters idle (EXIT_REASON_HLT case). STI instruction enables
- * interrupts only one instruction later. If there is a window between
- * STI and the instruction that emulates the HALT state, there is a
- * chance for interrupts to happen in this window, which can delay the
- * HLT operation indefinitely. Since this is the not the desired
- * result, conditionally call STI before TDCALL.
- */
- testq $TDX_HCALL_ISSUE_STI, %rsi
- jz .Lskip_sti
- sti
- .Lskip_sti:
- 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
- RET
- .Lpanic:
- call __tdx_hypercall_failed
- /* __tdx_hypercall_failed never returns */
- REACHABLE
- jmp .Lpanic
- SYM_FUNC_END(__tdx_hypercall)
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