On 24/01/2017 08:17, Pavel Dovgalyuk wrote: > This patch adds check to break cpu loop when icount expires without > setting the TB_EXIT_ICOUNT_EXPIRED flag. It happens when there is no > available translated blocks and all instructions were executed. > In icount replay mode unnecessary tb_find will be called (which may > cause an exception) and execution will be non-deterministic. > > Signed-off-by: Pavel Dovgalyuk <[email protected]> > --- > cpu-exec.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/cpu-exec.c b/cpu-exec.c > index 79a2167..e603da4 100644 > --- a/cpu-exec.c > +++ b/cpu-exec.c > @@ -582,9 +582,6 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, > TranslationBlock *tb, > cpu_exec_nocache(cpu, insns_left, *last_tb, false); > align_clocks(sc, cpu); > } > - cpu->exception_index = EXCP_INTERRUPT; > - *last_tb = NULL; > - cpu_loop_exit(cpu); > } > break; > #endif > @@ -638,6 +635,18 @@ int cpu_exec(CPUState *cpu) > > for(;;) { > cpu_handle_interrupt(cpu, &last_tb); > + /* icount has expired, we need to break the execution loop. > + This check is needed before tb_find to make execution > + deterministic - tb_find may cause an exception > + while translating the code from non-mapped page. */ > + if (use_icount && ((cpu->icount_extra == 0 > + && cpu->icount_decr.u16.low == 0) > + || (int32_t)cpu->icount_decr.u32 < 0)) { > + if (cpu->exception_index == -1) { > + cpu->exception_index = EXCP_INTERRUPT; > + } > + cpu_loop_exit(cpu); > + }
Can this can be placed in cpu_handle_interrupt itself? Also, can the cpu->exception_index != -1 case happen? We really should add assertions on cpu->exception_index, maybe after cpu_handle_exception and cc->cpu_exec_interrupt returns true. Without some idea of the invariants, I'm not competent enough to review this patch. Paolo > tb = tb_find(cpu, last_tb, tb_exit); > cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit, &sc); > /* Try to align the host and virtual clocks >
