Re: [Qemu-devel] [PULL 07/11] cpu-exec: don't overwrite exception_index

[Peter Maydell]

On 20 November 2017 at 11:06, Peter Maydell <address@hidden> wrote:
> On 20 November 2017 at 10:25, Pavel Dovgalyuk <address@hidden> wrote:
>>> From: Peter Maydell [mailto:address@hidden
>>> On 17 November 2017 at 20:26, Paolo Bonzini <address@hidden> wrote:
>>> > On 17/11/2017 21:07, Peter Maydell wrote:
>>> >> Hi. This commit breaks booting of Debian on aarch64 virt board.
>>> >> (repro instructions for creating the image available at:
>>> >> https://translatedcode.wordpress.com/2017/07/24/installing-debian-on-qemus-64-bit-arm-virt-
>>> board/)
>>> >> The guest kernel never prints anything to the serial port.
>>> >>
>>> >> Reverting this commit fixes master for me, so I plan to do
>>> >> that on Monday.
>>> >
>>> > Maybe you can also test moving the atomic_set inside the "if".  It does
>>> > seem to be a genuine bugfix.
>>>
>>> No, that doesn't help: guest still sits there like a lemon.
>>
>> Maybe this is a more complex problem?
>> I tried removing this if and aarch64 still does not work.
>
> Reverting the commit fixes it for me; I have that going through
> build tests and will push the revert later today.

Revert pushed to git master.

More generally, this commit seems to assume that QEMU always
does:
 * set exception_index to something
 * handle that
 * clear exception_index to -1

but it's not clear to me that it's actually always the case
that it gets cleared back to -1.

thanks
-- PMM