diff options
Diffstat (limited to 'arch/x86/virt/vmx/tdx/tdxcall.S')
| -rw-r--r-- | arch/x86/virt/vmx/tdx/tdxcall.S | 226 |
1 files changed, 175 insertions, 51 deletions
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S index 49a54356ae99..016a2a1ec1d6 100644 --- a/arch/x86/virt/vmx/tdx/tdxcall.S +++ b/arch/x86/virt/vmx/tdx/tdxcall.S @@ -1,5 +1,7 @@ /* SPDX-License-Identifier: GPL-2.0 */ #include <asm/asm-offsets.h> +#include <asm/frame.h> +#include <asm/asm.h> #include <asm/tdx.h> /* @@ -16,35 +18,75 @@ * TDX module and hypercalls to the VMM. * SEAMCALL - used by TDX hosts to make requests to the * TDX module. + * + *------------------------------------------------------------------------- + * TDCALL/SEAMCALL ABI: + *------------------------------------------------------------------------- + * Input Registers: + * + * RAX - TDCALL/SEAMCALL Leaf number. + * RCX,RDX,RDI,RSI,RBX,R8-R15 - TDCALL/SEAMCALL Leaf specific input registers. + * + * Output Registers: + * + * RAX - TDCALL/SEAMCALL instruction error code. + * RCX,RDX,RDI,RSI,RBX,R8-R15 - TDCALL/SEAMCALL Leaf specific output registers. + * + *------------------------------------------------------------------------- + * + * So while the common core (RAX,RCX,RDX,R8-R11) fits nicely in the + * callee-clobbered registers and even leaves RDI,RSI free to act as a + * base pointer, some leafs (e.g., VP.ENTER) make a giant mess of things. + * + * For simplicity, assume that anything that needs the callee-saved regs + * also tramples on RDI,RSI. This isn't strictly true, see for example + * TDH.EXPORT.MEM. */ -.macro TDX_MODULE_CALL host:req - /* - * R12 will be used as temporary storage for struct tdx_module_output - * pointer. Since R12-R15 registers are not used by TDCALL/SEAMCALL - * services supported by this function, it can be reused. - */ +.macro TDX_MODULE_CALL host:req ret=0 saved=0 + FRAME_BEGIN - /* Callee saved, so preserve it */ - push %r12 + /* Move Leaf ID to RAX */ + mov %rdi, %rax + + /* Move other input regs from 'struct tdx_module_args' */ + movq TDX_MODULE_rcx(%rsi), %rcx + movq TDX_MODULE_rdx(%rsi), %rdx + movq TDX_MODULE_r8(%rsi), %r8 + movq TDX_MODULE_r9(%rsi), %r9 + movq TDX_MODULE_r10(%rsi), %r10 + movq TDX_MODULE_r11(%rsi), %r11 +.if \saved /* - * Push output pointer to stack. - * After the operation, it will be fetched into R12 register. + * Move additional input regs from the structure. For simplicity + * assume that anything needs the callee-saved regs also tramples + * on RDI/RSI (see VP.ENTER). */ - push %r9 + /* Save those callee-saved GPRs as mandated by the x86_64 ABI */ + pushq %rbx + pushq %r12 + pushq %r13 + pushq %r14 + pushq %r15 - /* Mangle function call ABI into TDCALL/SEAMCALL ABI: */ - /* Move Leaf ID to RAX */ - mov %rdi, %rax - /* Move input 4 to R9 */ - mov %r8, %r9 - /* Move input 3 to R8 */ - mov %rcx, %r8 - /* Move input 1 to RCX */ - mov %rsi, %rcx - /* Leave input param 2 in RDX */ - - .if \host + movq TDX_MODULE_r12(%rsi), %r12 + movq TDX_MODULE_r13(%rsi), %r13 + movq TDX_MODULE_r14(%rsi), %r14 + movq TDX_MODULE_r15(%rsi), %r15 + movq TDX_MODULE_rbx(%rsi), %rbx + +.if \ret + /* Save the structure pointer as RSI is about to be clobbered */ + pushq %rsi +.endif + + movq TDX_MODULE_rdi(%rsi), %rdi + /* RSI needs to be done at last */ + movq TDX_MODULE_rsi(%rsi), %rsi +.endif /* \saved */ + +.if \host +.Lseamcall\@: seamcall /* * SEAMCALL instruction is essentially a VMExit from VMX root @@ -57,40 +99,122 @@ * This value will never be used as actual SEAMCALL error code as * it is from the Reserved status code class. */ - jnc .Lno_vmfailinvalid - mov $TDX_SEAMCALL_VMFAILINVALID, %rax -.Lno_vmfailinvalid: - - .else + jc .Lseamcall_vmfailinvalid\@ +.else tdcall - .endif +.endif +.if \ret +.if \saved /* - * Fetch output pointer from stack to R12 (It is used - * as temporary storage) + * Restore the structure from stack to save the output registers + * + * In case of VP.ENTER returns due to TDVMCALL, all registers are + * valid thus no register can be used as spare to restore the + * structure from the stack (see "TDH.VP.ENTER Output Operands + * Definition on TDCALL(TDG.VP.VMCALL) Following a TD Entry"). + * For this case, need to make one register as spare by saving it + * to the stack and then manually load the structure pointer to + * the spare register. + * + * Note for other TDCALLs/SEAMCALLs there are spare registers + * thus no need for such hack but just use this for all. */ - pop %r12 + pushq %rax /* save the TDCALL/SEAMCALL return code */ + movq 8(%rsp), %rax /* restore the structure pointer */ + movq %rsi, TDX_MODULE_rsi(%rax) /* save RSI */ + popq %rax /* restore the return code */ + popq %rsi /* pop the structure pointer */ + + /* Copy additional output regs to the structure */ + movq %r12, TDX_MODULE_r12(%rsi) + movq %r13, TDX_MODULE_r13(%rsi) + movq %r14, TDX_MODULE_r14(%rsi) + movq %r15, TDX_MODULE_r15(%rsi) + movq %rbx, TDX_MODULE_rbx(%rsi) + movq %rdi, TDX_MODULE_rdi(%rsi) +.endif /* \saved */ + /* Copy output registers to the structure */ + movq %rcx, TDX_MODULE_rcx(%rsi) + movq %rdx, TDX_MODULE_rdx(%rsi) + movq %r8, TDX_MODULE_r8(%rsi) + movq %r9, TDX_MODULE_r9(%rsi) + movq %r10, TDX_MODULE_r10(%rsi) + movq %r11, TDX_MODULE_r11(%rsi) +.endif /* \ret */ + +.if \saved && \ret /* - * Since this macro can be invoked with NULL as an output pointer, - * check if caller provided an output struct before storing output - * registers. + * Clear registers shared by guest for VP.VMCALL/VP.ENTER to prevent + * speculative use of guest's/VMM's values, including those are + * restored from the stack. + * + * See arch/x86/kvm/vmx/vmenter.S: * - * Update output registers, even if the call failed (RAX != 0). - * Other registers may contain details of the failure. + * In theory, a L1 cache miss when restoring register from stack + * could lead to speculative execution with guest's values. + * + * Note: RBP/RSP are not used as shared register. RSI has been + * restored already. + * + * XOR is cheap, thus unconditionally do for all leafs. */ - test %r12, %r12 - jz .Lno_output_struct - - /* Copy result registers to output struct: */ - movq %rcx, TDX_MODULE_rcx(%r12) - movq %rdx, TDX_MODULE_rdx(%r12) - movq %r8, TDX_MODULE_r8(%r12) - movq %r9, TDX_MODULE_r9(%r12) - movq %r10, TDX_MODULE_r10(%r12) - movq %r11, TDX_MODULE_r11(%r12) - -.Lno_output_struct: - /* Restore the state of R12 register */ - pop %r12 + xorl %ecx, %ecx + xorl %edx, %edx + xorl %r8d, %r8d + xorl %r9d, %r9d + xorl %r10d, %r10d + xorl %r11d, %r11d + xorl %r12d, %r12d + xorl %r13d, %r13d + xorl %r14d, %r14d + xorl %r15d, %r15d + xorl %ebx, %ebx + xorl %edi, %edi +.endif /* \ret && \host */ + +.if \host +.Lout\@: +.endif + +.if \saved + /* Restore callee-saved GPRs as mandated by the x86_64 ABI */ + popq %r15 + popq %r14 + popq %r13 + popq %r12 + popq %rbx +.endif /* \saved */ + + FRAME_END + RET + +.if \host +.Lseamcall_vmfailinvalid\@: + mov $TDX_SEAMCALL_VMFAILINVALID, %rax + jmp .Lseamcall_fail\@ + +.Lseamcall_trap\@: + /* + * SEAMCALL caused #GP or #UD. By reaching here RAX contains + * the trap number. Convert the trap number to the TDX error + * code by setting TDX_SW_ERROR to the high 32-bits of RAX. + * + * Note cannot OR TDX_SW_ERROR directly to RAX as OR instruction + * only accepts 32-bit immediate at most. + */ + movq $TDX_SW_ERROR, %rdi + orq %rdi, %rax + +.Lseamcall_fail\@: +.if \ret && \saved + /* pop the unused structure pointer back to RSI */ + popq %rsi +.endif + jmp .Lout\@ + + _ASM_EXTABLE_FAULT(.Lseamcall\@, .Lseamcall_trap\@) +.endif /* \host */ + .endm |