diff options
Diffstat (limited to 'tools/testing/selftests/kvm/x86_64/sync_regs_test.c')
| -rw-r--r-- | tools/testing/selftests/kvm/x86_64/sync_regs_test.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c index 11c2a70a7b87..5c8224256294 100644 --- a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c +++ b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c @@ -22,18 +22,19 @@ #define VCPU_ID 5 +#define UCALL_PIO_PORT ((uint16_t)0x1000) + +/* + * ucall is embedded here to protect against compiler reshuffling registers + * before calling a function. In this test we only need to get KVM_EXIT_IO + * vmexit and preserve RBX, no additional information is needed. + */ void guest_code(void) { - /* - * use a callee-save register, otherwise the compiler - * saves it around the call to GUEST_SYNC. - */ - register u32 stage asm("rbx"); - for (;;) { - GUEST_SYNC(0); - stage++; - asm volatile ("" : : "r" (stage)); - } + asm volatile("1: in %[port], %%al\n" + "add $0x1, %%rbx\n" + "jmp 1b" + : : [port] "d" (UCALL_PIO_PORT) : "rax", "rbx"); } static void compare_regs(struct kvm_regs *left, struct kvm_regs *right) |