Re: [PATCH v2] exec: flush the whole TLB if a watchpoint crosses a page boundary

["Alex Bennée" <alex.bennee@linaro.org>]

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> On 6/3/20 2:46 PM, Philippe Mathieu-Daudé wrote:
>> On 6/3/20 1:24 PM, Alex Bennée wrote:
>>> There is no particular reason why you can't have a watchpoint in TCG
>>> that covers a large chunk of the address space. We could be clever
>>> about it but these cases are pretty rare and we can assume the user
>>> will expect a little performance degradation.
>>>
>>> NB: In my testing gdb will silently squash a watchpoint like:
>>>
>>>   watch (char[0x7fffffffff]) *0x0
>>>
>>> to a 4 byte watchpoint. Practically it will limit the maximum size
>>> based on max-value-size. However given enough of a tweak the sky is
>>> the limit.
>>>
>>> Reported-by: Alexander Bulekov <alxndr@bu.edu>
>>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>>>
>>> ---
>>> v2
>>>   - use cleaner in_page = -(addr | TARGET_PAGE_MASK) logic per rth
>> 
>> Can we have a macro for this?
>> Maybe QEMU_IN_PAGE_OFFSET(addr, TARGET_PAGE_MASK)?
>> or QEMU_OFFSET_IN_PAGE()...
>
> As this is queued, I suppose the implicit answer is "no."

Richard took it into tcg/next as is. I think having a macro may well be
nice clean-up but I struggled to pick a good include location so left it
for a future clean-up series ;-)

-- 
Alex Bennée