Re: [Qemu-discuss] ppc and icount

[Peter Maydell]

On 10 January 2018 at 08:57, Steven Seeger
<address@hidden> wrote:
> Sorry for another post. I did a bisect and found what is the bad commit for
> me:
>
> 044897ef4a22af89aecb8df509477beba0a2e0ce is the first bad commit
> commit 044897ef4a22af89aecb8df509477beba0a2e0ce
> Author: Richard Purdie <address@hidden>
> Date:   Mon Dec 4 22:25:43 2017 +0000
>
>     target/ppc: Fix system lockups caused by interrupt_request state
> corruption

Great -- thanks for the bisect. Let's take this to the -devel list;
I've cc'd the PPC maintainers.

Context: Steven reports that we broke -icount for PPC guests with
this commit:

$ ./build/all/ppc-softmmu/qemu-system-ppc  -icount auto
qemu: fatal: Raised interrupt while not in I/O function
NIP fff08978   LR fff08904 CTR 00000000 XER 00000000 CPU#0
MSR 00000000 HID0 00000000  HF 00000000 iidx 3 didx 3
Bad icount read

The backtrace from the assert is:

#0  tcg_handle_interrupt (cpu=0x7ffff7fc2010, mask=4) at qemu/accel/tcg/tcg-
all.c:58
#1  0x0000555555962aa4 in cpu_interrupt (cpu=0x7ffff7fc2010, mask=4) at qemu/
include/qom/cpu.h:859
#2  0x0000555555962e55 in cpu_interrupt_exittb (cs=0x7ffff7fc2010) at qemu/
target/ppc/helper_regs.h:105
#3  0x0000555555964505 in do_rfi (env=0x7ffff7fca2b0, nip=197460, msr=4096)
    at qemu/target/ppc/excp_helper.c:998
#4  0x0000555555964555 in helper_rfi (env=0x7ffff7fca2b0) at qemu/target/ppc/
excp_helper.c:1008
#5  0x00007fffe7c124b9 in code_gen_buffer ()

The problem is that icount was relying on the previous
handling of do_rfi() as "just set state as we know we're
going to be last insn in the TB".

Not sure how best to fix this (mark the insn as IO ok?)

thanks
-- PMM