Re: [Qemu-devel] [PATCH] TCG: Fix TB invalidation after breakpoint insertion/deletion

[Max Filippov]

On Thu, May 24, 2012 at 4:16 PM, Jan Kiszka <address@hidden> wrote:
> On 2012-05-24 09:08, Max Filippov wrote:
>> On Thu, May 24, 2012 at 3:25 PM, Jan Kiszka <address@hidden> wrote:
>>> On 2012-05-24 07:51, Max Filippov wrote:
>>>> On Thu, May 24, 2012 at 6:34 AM, Jan Kiszka <address@hidden> wrote:
>>>>> From: Jan Kiszka <address@hidden>
>>>>>
>>>>> tb_invalidate_phys_addr has to called with the exact physical address of
>>>>> the breakpoint we add/remove, not just the page's base address.
>>>>> Otherwise we easily fail to flush the right TB.
>>>>>
>>>>> Regression of 1e7855a558.
>>>>
>>>> Sorry, I fail to see how 1e7855a558 could introduce a regression, it
>>>> just rearranged the code.
>>>> Even more, AFAIK cpu_get_phys_page_debug returns complete physical
>>>> address, not just
>>>> physical page. Probably it has a misleading name.
>>>
>>> Unfortunately, cpu_get_phys_page_debug does NOT deliver the sub-page
>>> offset, only the page base address.
>>
>> Ok, i386 has probably the most explicit implementation,
>> let's look at the target-i386/helper.c:876
>>
>>     page_offset = (addr & TARGET_PAGE_MASK) & (page_size - 1);
>>     paddr = (pte & TARGET_PAGE_MASK) + page_offset;
>>     return paddr;
>>
>> that's clearly physical page plus in-page offset.
>> I can provide other samples (:
>
> "page_offset" is misleading: addr & TARGET_PAGE_MASK kills all the
> offset bits. It will only contain the relevant bits between page_size
> and TARGET_PAGE_SIZE.
>
> Check also ppc's cpu_get_phys_page_debug, it's clearer in this regard.

Ok, for i386, ppc, microblaze (and maybe others) you're right.
What about ARM, CRIS, MIPS, SH4, xtensa (and maybe others)?
Looks like this is a long-standing discrepancy and consequently
a long-standing bug in the breakpoint_invalidate.

-- 
Thanks.
-- Max