Add a helper to detect whether or not KVM's forced emulation prefix is
available. Use the helper to replace equivalent functionality in the
emulator test.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
lib/x86/desc.h | 14 ++++++++++++++
x86/emulator.c | 15 +--------------
2 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index 8f708fd..c023b93 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -106,6 +106,20 @@ typedef struct __attribute__((packed)) {
#define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
#define ASM_TRY_FEP(catch) __ASM_TRY(KVM_FEP, catch)
+static inline bool is_fep_available(void)
+{
+ /*
+ * Use the non-FEP ASM_TRY() as KVM will inject a #UD on the prefix
+ * itself if forced emulation is not available.
+ */
+ asm goto(ASM_TRY("%l[fep_unavailable]")
+ KVM_FEP "nop\n\t"
+ ::: "memory" : fep_unavailable);
+ return true;
+fep_unavailable:
+ return false;
+}
+
/*
* selector 32-bit 64-bit
* 0x00 NULL descriptor NULL descriptor
diff --git a/x86/emulator.c b/x86/emulator.c
index 6dc88f1..e1272a6 100644
--- a/x86/emulator.c
+++ b/x86/emulator.c
@@ -17,10 +17,6 @@
static int exceptions;
-/* Forced emulation prefix, used to invoke the emulator unconditionally. */
-#define KVM_FEP_LENGTH 5
-static int fep_available = 1;
-
struct regs {
u64 rax, rbx, rcx, rdx;
u64 rsi, rdi, rsp, rbp;
@@ -1121,12 +1117,6 @@ static void test_illegal_movbe(void)
handle_exception(UD_VECTOR, 0);
}
-static void record_no_fep(struct ex_regs *regs)
-{
- fep_available = 0;
- regs->rip += KVM_FEP_LENGTH;
-}
-
int main(void)
{
void *mem;
@@ -1136,9 +1126,6 @@ int main(void)
unsigned long t1, t2;
setup_vm();
- handle_exception(UD_VECTOR, record_no_fep);
- asm(KVM_FEP "nop");
- handle_exception(UD_VECTOR, 0);
mem = alloc_vpages(2);
install_page((void *)read_cr3(), IORAM_BASE_PHYS, mem);
@@ -1190,7 +1177,7 @@ int main(void)
test_ltr(mem);
test_cmov(mem);
- if (fep_available) {
+ if (is_fep_available()) {
test_mmx_movq_mf(mem);
test_movabs(mem);
test_smsw_reg(mem);
--
2.37.1.559.g78731f0fdb-goog
