Re: [Qemu-devel] [PATCH] target-*: Advance pc after recognizing a breakpoint

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

On 16.10.2015 17:08, Sergey Fedorov wrote:
> On 16.10.2015 04:14, Richard Henderson wrote:
>> On 10/16/2015 03:36 AM, Peter Maydell wrote:
>>> On 14 October 2015 at 22:02, Richard Henderson <rth@twiddle.net> wrote:
>>>> On 10/15/2015 06:34 AM, Peter Maydell wrote:
>>>>> This is still the same cryptic comment we have in the
>>>>> targets which do do this. Can we have something
>>>>> that is a bit more explanatory about what is going on and
>>>>> why we need to do this, please?
>>>>
>>>> Suggestions?
>>> ...well, I don't entirely understand the problem it's
>>> fixing, which is why I'm asking for a better comment :-)
>> Heh.  Fair enough.  How about
>>
>>   /* The address covered by the breakpoint must be included in
>>      [tb->pc, tb->pc + tb->size) in order to for it to be
>>      properly cleared -- thus we increment the PC here so that
>>      the logic setting tb->size below does the right thing.  */
>>
>> There are two edge cases that cause the problem with clearing that
>> could be described, but I think that the comment becomes too bulky, as
>> well as confuses the situation for someone cutting-and-pasting the
>> logic to a new port.
> Maybe we could rather fix that condition in
> tb_invalidate_phys_page_range()? It seems weird that it can't handle a
> zero-sized TB.

I think extending "!(tb_end <= start || tb_start >= end)" condition to
"!(tb_end <= start || tb_start >= end) || tb_start == start" would work
fine. Thoughts? I could prepare a patch for that.

Best regards,
Sergey