From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43649) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eOORH-0004UV-QF for qemu-devel@nongnu.org; Mon, 11 Dec 2017 08:48:12 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eOORG-0007Ll-TX for qemu-devel@nongnu.org; Mon, 11 Dec 2017 08:48:11 -0500 From: David Hildenbrand Date: Mon, 11 Dec 2017 14:47:32 +0100 Message-Id: <20171211134740.8235-8-david@redhat.com> In-Reply-To: <20171211134740.8235-1-david@redhat.com> References: <20171211134740.8235-1-david@redhat.com> Subject: [Qemu-devel] [PATCH v1 for-2-12 07/15] s390x/tcg: tolerate wrong wakeups due to floating interrupts List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-s390x@nongnu.org, qemu-devel@nongnu.org Cc: Christian Borntraeger , Cornelia Huck , Richard Henderson , Alexander Graf , Paolo Bonzini , Peter Crosthwaite , Thomas Huth , David Hildenbrand This is a preparation for floating interrupt support and only applies to MTTCG, single threaded TCG works just fine. If a floating interrupt wakes up a VCPU and the CPU thinks it can run (clearing cs->halted), at the point where the interrupt would be delivered, already another VCPU might have picked up the interrupt, resulting in a wakeup without an interrupt (executing wrong code). It is wrong to let the VCPU continue to execute (the WAIT PSW). Instead, we have to put the VCPU back to sleep. Signed-off-by: David Hildenbrand --- target/s390x/excp_helper.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c index a18842ccbd..eeffb49f63 100644 --- a/target/s390x/excp_helper.c +++ b/target/s390x/excp_helper.c @@ -503,6 +503,11 @@ bool s390_cpu_exec_interrupt(CPUState *cs, int interrupt_request) s390_cpu_do_interrupt(cs); return true; } + if (env->psw.mask & PSW_MASK_WAIT) { + /* Woken up because of a floating interrupt but it has already + * been delivered. Go back to sleep. */ + cpu_interrupt(CPU(cpu), CPU_INTERRUPT_HALT); + } } return false; } -- 2.14.3