On Fri, Aug 10, 2012 at 10:06 PM, Peter Maydell
<peter.mayd...@linaro.org> wrote:
> On 10 August 2012 19:53, Steven <wangwangk...@gmail.com> wrote:
>> On Fri, Aug 10, 2012 at 11:47 AM, Peter Maydell
>> <peter.mayd...@linaro.org> wrote:
>>> On 10 August 2012 03:11, Steven <wangwangk...@gmail.com> wrote:
>>>> The function definition has a return address type tb_page_addr_t.
>>>> tb_page_addr_t get_page_addr_code(CPUArchState *env1, target_ulong addr)
>>>>
>>>> I am wondering is this address the guest physical address or the host
>>>> virtual address.
>>>
>>> In linux-user mode the returned address is the guest virtual address.
>>> In system mode it is a ram_addr_t. (the comment above the implementation
>>> says "the returned address is not exactly the physical address: it
>>> is the offset relative to phys_ram_base" but this is out of date I think).
>>> A ram_addr_t is neither a host address nor a guest physical address
>>> but it's closely related to a guest physaddr (you can think of it as
>>> if all the RAM in the system was put into a straight line and then the
>>
>> My question is related to system mode.
>> Is the RAM you mean the guest physical address, which is a continuous
>> sequence of numbers beginning from 0 to the max of allocated RAM of
>> the guest?
>>
>>> ram_addr_t is an index into that).
>>
>> If the returned value of get_page_addr_code is the index to that
>> straight line, I am wondering if it is the guest physical address.
>
> No, it is definitely not the guest physical address. Consider
> the case where there are two aliases of the same RAM in
> guest physical memory -- two physical addresses might
> map to a single ram_addr_t. Consider the case where there
> is a 'hole' in memory -- ram_addr_t and physical address are
> not identical there either.
>
>> So if I want to get the guest physical address (GPA) of a
>> tb_page_addr_t, can I do
>> tb_page_addr_t = returned value from get_page_addr_code + phys_ram_base
>> Is this translation correct?
>
> This is wrong on several counts: (a) there's no such thing
> as phys_ram_base any more (it was removed several years
> ago) and (b) there is no single unique guest physical
> address corresponding to a tb_page_addr_t, so what
> you are trying to do is not well defined.
>
> What are you trying to do anyway and why do you want
> to call get_page_addr_code() ?
>
> -- PMM
I want to get the guest physical address of a pc. I note the part of
the function cpu_x86_handle_mmu_fault will do something like page
walking to convert a pc to its guest physical address. I think this is
the guest physical address I need. However, there is no other function
available to do this page walking.
So I am thinking add a function to do the conversion.
After you mentions about the memory region, do you think the following
formula is correct
guest_physical address = block->mr->addr + (pc's host virtual
address - block->host)
^
^
Base of the mapped memory block
(offset in the memory block)
Or do you have any suggestion? Thanks.
