From: Christian Borntraeger Date: Thu, 10 Oct 2019 07:37:29 +0000 (+0200) Subject: selftests: kvm: make syncregs more reliable on s390 X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=efec8d219fb1bc2d7ab4f1c582e7beed44e309f4;p=linux.git 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 Suggested-by: Paolo Bonzini Reviewed-by: Thomas Huth --- 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) \