> -----Original Message----- > From: Hollis Blanchard [mailto:hollisb@xxxxxxxxxx] > Sent: Wednesday, May 06, 2009 3:21 AM > To: Liu Yu-B13201 > Subject: single-step issue > > The e500 user manual (section 5.11.1, e500 Exception Priorities) says > that Debug interrupts have higher priority than Program interrupts. > However, that only matters if both exceptions exist at the same time, > which I don't think is true in this case. > > Ordinarily, the debug interrupt should occur *after* the > effects of the > instruction have occurred. So I would expect that, when > single-stepping > through a privileged guest instruction, you would get the program > interrupt simply because the instruction can't be executed (therefore > the debug interrupt couldn't possibly occur). That matches > the behavior > you've seen, correct? > > Solution: after emulate_instruction() in the Program handler succeeds, > check vcpu->your_debug_flags to see if control should return > to qemu/gdb > instead of back to the guest. > Sorry for the late reply, I got some urgent work to deal with. Yes. I should use CSRR0 to get next pc in single-step mode. And it works well in normal case. The problem I met is that when guest meet a privilege instructions, The CSRR0 give out a strange address which should not be used to enter into guest. And I find it out now. When guest meet a privilege instructions, first the program interrupt occurs, but immediately after it, a debug interrupt occurs, and the CSRR0 is filled with the value of "kvmppc_booke_handlers + ivor[IVOR6]" (kvmppc program interrupt handler), which is indeed the next instruction of guest privilege instruction.... I guess the reason is that program interrupt doesn't clear MSR[DE] bit, right? If so, then we cannot check vcpu->debug_flags to see if control should return to qemu/gdb. Should we emulate privilege instructions in debug interrupt handler? One thing I still don't get clear is that: does MSR[DE] is set while running guest? I see nowhere set it, but all kinds of debug interrupt seem could work. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
