From efec8d219fb1bc2d7ab4f1c582e7beed44e309f4 Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Thu, 10 Oct 2019 09:37:29 +0200
Subject: [PATCH] selftests: kvm: make syncregs more reliable on s390
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@de.ibm.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
.../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 d5290b4ad6360..b705637ca14b6 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 doing a ucall to avoid that
+ * the compiler has messed with r11 at the time of the ucall.
+ */
+ asm volatile (
+ "0: diag 0,0,0x501\n"
+ " ahi 11,1\n"
+ " j 0b\n"
+ );
}
#define REG_COMPARE(reg) \