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

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-05-24 09:08, Max Filippov wrote:
> On Thu, May 24, 2012 at 3:25 PM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>> On 2012-05-24 07:51, Max Filippov wrote:
>>> On Thu, May 24, 2012 at 6:34 AM, Jan Kiszka <jan.kiszka@web.de> wrote:
>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>>
>>>> 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.

Jan

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