similar to commit 2c57da356800 ("selftests: kvm: fix sync_regs_test with
newer gccs") and commit 204c91eff798a ("KVM: selftests: do not blindly
clobber registers in guest asm") we better do not rely on gcc leaving
r11 untouched. We can write the simple ucall inline and have the guest
code completely as small assembler function.
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
.../testing/selftests/kvm/s390x/sync_regs_test.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/kvm/s390x/sync_regs_test.c b/tools/testing/selftests/kvm/s390x/sync_regs_test.c
index d5290b4ad636..04d6abe68961 100644
--- a/tools/testing/selftests/kvm/s390x/sync_regs_test.c
+++ b/tools/testing/selftests/kvm/s390x/sync_regs_test.c
@@ -25,12 +25,15 @@
static void guest_code(void)
{
- register u64 stage asm("11") = 0;
-
- for (;;) {
- GUEST_SYNC(0);
- asm volatile ("ahi %0,1" : : "r"(stage));
- }
+ /*
+ * we embed diag 501 here instead of a ucall as the called function
+ * could mess with the content of r11 when doing the hypercall
+ */
+ asm volatile (
+ "0: diag 0,0,0x501\n"
+ " ahi 11,1\n"
+ " j 0b\n"
+ );
}
#define REG_COMPARE(reg) \
--
2.21.0
