KVM: selftests: Add a forced emulation variation of KVM_ASM_SAFE()

Add KVM_ASM_SAFE_FEP() to allow forcing emulation on an instruction that
might fault.  Note, KVM skips RIP past the FEP prefix before injecting an
exception, i.e. the fixup needs to be on the instruction itself.  Do not
check for FEP support, that is firmly the responsibility of whatever code
wants to use KVM_ASM_SAFE_FEP().

Sadly, chaining variadic arguments that contain commas doesn't work, thus
the unfortunate amount of copy+paste.

Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-28-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -1154,16 +1154,19 @@ void vm_install_exception_handler(struct kvm_vm *vm, int vector,
  * r9  = exception vector (non-zero)
  * r10 = error code
  */
-#define KVM_ASM_SAFE(insn)					\
+#define __KVM_ASM_SAFE(insn, fep)				\
 	"mov $" __stringify(KVM_EXCEPTION_MAGIC) ", %%r9\n\t"	\
 	"lea 1f(%%rip), %%r10\n\t"				\
 	"lea 2f(%%rip), %%r11\n\t"				\
-	"1: " insn "\n\t"					\
+	fep "1: " insn "\n\t"					\
 	"xor %%r9, %%r9\n\t"					\
 	"2:\n\t"						\
 	"mov  %%r9b, %[vector]\n\t"				\
 	"mov  %%r10, %[error_code]\n\t"
 
+#define KVM_ASM_SAFE(insn) __KVM_ASM_SAFE(insn, "")
+#define KVM_ASM_SAFE_FEP(insn) __KVM_ASM_SAFE(insn, KVM_FEP)
+
 #define KVM_ASM_SAFE_OUTPUTS(v, ec)	[vector] "=qm"(v), [error_code] "=rm"(ec)
 #define KVM_ASM_SAFE_CLOBBERS	"r9", "r10", "r11"
 
@@ -1190,6 +1193,29 @@ void vm_install_exception_handler(struct kvm_vm *vm, int vector,
 	vector;								\
 })
 
+#define kvm_asm_safe_fep(insn, inputs...)				\
+({									\
+	uint64_t ign_error_code;					\
+	uint8_t vector;							\
+									\
+	asm volatile(KVM_ASM_SAFE(insn)					\
+		     : KVM_ASM_SAFE_OUTPUTS(vector, ign_error_code)	\
+		     : inputs						\
+		     : KVM_ASM_SAFE_CLOBBERS);				\
+	vector;								\
+})
+
+#define kvm_asm_safe_ec_fep(insn, error_code, inputs...)		\
+({									\
+	uint8_t vector;							\
+									\
+	asm volatile(KVM_ASM_SAFE_FEP(insn)				\
+		     : KVM_ASM_SAFE_OUTPUTS(vector, error_code)		\
+		     : inputs						\
+		     : KVM_ASM_SAFE_CLOBBERS);				\
+	vector;								\
+})
+
 static inline uint8_t rdmsr_safe(uint32_t msr, uint64_t *val)
 {
 	uint64_t error_code;