Re: [Qemu-devel] [PULL 13/13] target-arm: Fix CPU breakpoint handling

[Sergey Fedorov <serge.fdrv@gmail.com>]

On 02.11.2015 14:09, Peter Maydell wrote:
> On 21 October 2015 at 19:15, Sergey Fedorov <serge.fdrv@gmail.com> wrote:
>> On 16.10.2015 16:58, Peter Maydell wrote:
>>> From: Sergey Fedorov <serge.fdrv@gmail.com>
>>>
>>> A QEMU breakpoint match is not definitely an architectural breakpoint
>>> match. If an exception is generated unconditionally during translation,
>>> it is hardly possible to ignore it in the debug exception handler.
>>>
>>> Generate a call to a helper to check CPU breakpoints and raise an
>>> exception only if any breakpoint matches architecturally.
>>>
>>> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
>>> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>>> ---
>> It turns out that this change introduced an issue which can be
>> illustrated by the following test:
>> I think we could fix this problem by cleaning up DISAS_UPDATE usage in
>> target-arm/translate.c and implementing PC update as in
>> target-arm/translate-a64.c. I could prepare a patch for that.
>>
>> Another problem, I think, is that we should somehow restore the CPU
>> state before raising an exception from check_breakpoints() helper. But
>> so far I have no idea how to fix this...
> Hi, Sergey -- how are you doing with the fix for this? It would
> be good to get it in and tested soon, because hardfreeze is next
> week.
>
> I've also had a report that this patch broke gdbstub single-stepping,
> which might be the same underlying cause.

Hi Peter,

The patch for DISAS_UPDATE is almost ready. Basically, all I need is to
prepare a commit message. But I'm not sure how to deal with CPU state
restoring issue. Also it's a strange thing about gdbstub single-stepping
I'm going to look at it.

Best,
Sergey