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

[Peter Maydell]

On 21 October 2015 at 19:15, Sergey Fedorov <address@hidden> wrote:
> On 16.10.2015 16:58, Peter Maydell wrote:
>> From: Sergey Fedorov <address@hidden>
>>
>> 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 <address@hidden>
>> Reviewed-by: Peter Maydell <address@hidden>
>> Signed-off-by: Peter Maydell <address@hidden>
>> ---

> 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.

thanks
-- PMM