From: Nicholas Piggin Date: Tue, 29 Aug 2023 01:06:58 +0000 (+1000) Subject: accel/tcg: mttcg remove false-negative halted assertion X-Git-Tag: v8.1.2~43 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b9b84b2d4190eef78fffdb1f1063e3e37ebbc91a;p=thirdparty%2Fqemu.git accel/tcg: mttcg remove false-negative halted assertion mttcg asserts that an execution ending with EXCP_HALTED must have cpu->halted. However between the event or instruction that sets cpu->halted and requests exit and the assertion here, an asynchronous event could clear cpu->halted. This leads to crashes running AIX on ppc/pseries because it uses H_CEDE/H_PROD hcalls, where H_CEDE sets self->halted = 1 and H_PROD sets other cpu->halted = 0 and kicks it. H_PROD could be turned into an interrupt to wake, but several other places in ppc, sparc, and semihosting follow what looks like a similar pattern setting halted = 0 directly. So remove this assertion. Reported-by: Ivan Warren Signed-off-by: Nicholas Piggin Message-Id: <20230829010658.8252-1-npiggin@gmail.com> [rth: Keep the case label and adjust the comment.] Signed-off-by: Richard Henderson (cherry picked from commit 0e5903436de712844b0e6cdd862b499c767e09e9) Signed-off-by: Michael Tokarev --- diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c index b2762620079..4b0dfb4be73 100644 --- a/accel/tcg/tcg-accel-ops-mttcg.c +++ b/accel/tcg/tcg-accel-ops-mttcg.c @@ -100,14 +100,9 @@ static void *mttcg_cpu_thread_fn(void *arg) break; case EXCP_HALTED: /* - * during start-up the vCPU is reset and the thread is - * kicked several times. If we don't ensure we go back - * to sleep in the halted state we won't cleanly - * start-up when the vCPU is enabled. - * - * cpu->halted should ensure we sleep in wait_io_event + * Usually cpu->halted is set, but may have already been + * reset by another thread by the time we arrive here. */ - g_assert(cpu->halted); break; case EXCP_ATOMIC: qemu_mutex_unlock_iothread();