From: Isaku Yamahata <[email protected]>
TDX defines an API to run TDX vcpu with its own ABI. Define an assembly
helper function to run TDX vcpu to hide the special ABI so that C code can
call it with function call ABI.
Signed-off-by: Isaku Yamahata <[email protected]>
---
arch/x86/include/asm/tdx.h | 3 +-
arch/x86/kvm/vmx/vmenter.S | 156 +++++++++++++++++++++++++++++++++++++
2 files changed, 158 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 97492b69e93f..d2d41bc452fd 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -16,7 +16,8 @@
* Bits 47:40 == 0xFF indicate Reserved status code class that never used by
* TDX module.
*/
-#define TDX_ERROR _BITUL(63)
+#define TDX_ERROR_BIT 63
+#define TDX_ERROR _BITUL(TDX_ERROR_BIT)
#define TDX_SW_ERROR (TDX_ERROR | GENMASK_ULL(47, 40))
#define TDX_SEAMCALL_VMFAILINVALID (TDX_SW_ERROR | _UL(0xFFFF0000))
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 631fd7da2bc3..ae93a576e934 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -6,6 +6,7 @@
#include <asm/nospec-branch.h>
#include <asm/percpu.h>
#include <asm/segment.h>
+#include <asm/tdx.h>
#include "kvm-asm-offsets.h"
#include "run_flags.h"
@@ -31,6 +32,12 @@
#define VCPU_R15 __VCPU_REGS_R15 * WORD_SIZE
#endif
+#ifdef CONFIG_INTEL_TDX_HOST
+#define TDH_VP_ENTER 0
+#define EXIT_REASON_TDCALL 77
+#define seamcall .byte 0x66,0x0f,0x01,0xcf
+#endif
+
.macro VMX_DO_EVENT_IRQOFF call_insn call_target
/*
* Unconditionally create a stack frame, getting the correct RSP on the
@@ -360,3 +367,152 @@ SYM_FUNC_END(vmread_error_trampoline)
SYM_FUNC_START(vmx_do_interrupt_irqoff)
VMX_DO_EVENT_IRQOFF CALL_NOSPEC _ASM_ARG1
SYM_FUNC_END(vmx_do_interrupt_irqoff)
+
+#ifdef CONFIG_INTEL_TDX_HOST
+
+.pushsection .noinstr.text, "ax"
+
+/**
+ * __tdx_vcpu_run - Call SEAMCALL(TDH_VP_ENTER) to run a TD vcpu
+ * @tdvpr: physical address of TDVPR
+ * @regs: void * (to registers of TDVCPU)
+ * @gpr_mask: non-zero if guest registers need to be loaded prior to TDH_VP_ENTER
+ *
+ * Returns:
+ * TD-Exit Reason
+ *
+ * Note: KVM doesn't support using XMM in its hypercalls, it's the HyperV
+ * code's responsibility to save/restore XMM registers on TDVMCALL.
+ */
+SYM_FUNC_START(__tdx_vcpu_run)
+ push %rbp
+ mov %rsp, %rbp
+
+ push %r15
+ push %r14
+ push %r13
+ push %r12
+ push %rbx
+
+ /* Save @regs, which is needed after TDH_VP_ENTER to capture output. */
+ push %rsi
+
+ /* Load @tdvpr to RCX */
+ mov %rdi, %rcx
+
+ /* No need to load guest GPRs if the last exit wasn't a TDVMCALL. */
+ test %dx, %dx
+ je 1f
+
+ /* Load @regs to RAX, which will be clobbered with $TDH_VP_ENTER anyways. */
+ mov %rsi, %rax
+
+ mov VCPU_RBX(%rax), %rbx
+ mov VCPU_RDX(%rax), %rdx
+ mov VCPU_RBP(%rax), %rbp
+ mov VCPU_RSI(%rax), %rsi
+ mov VCPU_RDI(%rax), %rdi
+
+ mov VCPU_R8 (%rax), %r8
+ mov VCPU_R9 (%rax), %r9
+ mov VCPU_R10(%rax), %r10
+ mov VCPU_R11(%rax), %r11
+ mov VCPU_R12(%rax), %r12
+ mov VCPU_R13(%rax), %r13
+ mov VCPU_R14(%rax), %r14
+ mov VCPU_R15(%rax), %r15
+
+ /* Load TDH_VP_ENTER to RAX. This kills the @regs pointer! */
+1: mov $TDH_VP_ENTER, %rax
+
+2: seamcall
+
+ /*
+ * Use same return value convention to tdxcall.S.
+ * TDX_SEAMCALL_VMFAILINVALID doesn't conflict with any TDX status code.
+ */
+ jnc 3f
+ mov $TDX_SEAMCALL_VMFAILINVALID, %rax
+ jmp 5f
+3:
+
+ /* Skip to the exit path if TDH_VP_ENTER failed. */
+ bt $TDX_ERROR_BIT, %rax
+ jc 5f
+
+ /* Temporarily save the TD-Exit reason. */
+ push %rax
+
+ /* check if TD-exit due to TDVMCALL */
+ cmp $EXIT_REASON_TDCALL, %ax
+
+ /* Reload @regs to RAX. */
+ mov 8(%rsp), %rax
+
+ /* Jump on non-TDVMCALL */
+ jne 4f
+
+ /* Save all output from SEAMCALL(TDH_VP_ENTER) */
+ mov %rbx, VCPU_RBX(%rax)
+ mov %rbp, VCPU_RBP(%rax)
+ mov %rsi, VCPU_RSI(%rax)
+ mov %rdi, VCPU_RDI(%rax)
+ mov %r10, VCPU_R10(%rax)
+ mov %r11, VCPU_R11(%rax)
+ mov %r12, VCPU_R12(%rax)
+ mov %r13, VCPU_R13(%rax)
+ mov %r14, VCPU_R14(%rax)
+ mov %r15, VCPU_R15(%rax)
+
+4: mov %rcx, VCPU_RCX(%rax)
+ mov %rdx, VCPU_RDX(%rax)
+ mov %r8, VCPU_R8 (%rax)
+ mov %r9, VCPU_R9 (%rax)
+
+ /*
+ * Clear all general purpose registers except RSP and RAX to prevent
+ * speculative use of the guest's values.
+ */
+ xor %rbx, %rbx
+ xor %rcx, %rcx
+ xor %rdx, %rdx
+ xor %rsi, %rsi
+ xor %rdi, %rdi
+ xor %rbp, %rbp
+ xor %r8, %r8
+ xor %r9, %r9
+ xor %r10, %r10
+ xor %r11, %r11
+ xor %r12, %r12
+ xor %r13, %r13
+ xor %r14, %r14
+ xor %r15, %r15
+
+ /* Restore the TD-Exit reason to RAX for return. */
+ pop %rax
+
+ /* "POP" @regs. */
+5: add $8, %rsp
+ pop %rbx
+ pop %r12
+ pop %r13
+ pop %r14
+ pop %r15
+
+ pop %rbp
+ RET
+
+6: cmpb $0, kvm_rebooting
+ je 1f
+ mov $TDX_SW_ERROR, %r12
+ orq %r12, %rax
+ jmp 5b
+1: ud2
+ /* Use FAULT version to know what fault happened. */
+ _ASM_EXTABLE_FAULT(2b, 6b)
+
+SYM_FUNC_END(__tdx_vcpu_run)
+
+.popsection
+
+#endif
--
2.25.1