Re: [Xen-devel] Little help with Seabios PV-Drivers for XEN

[Daniel Castro <evil.dani@xxxxxxxxx>]

On Sat, Apr 7, 2012 at 5:34 AM, Konrad Rzeszutek Wilk
<konrad.wilk@xxxxxxxxxx> wrote:
> On Fri, Mar 09, 2012 at 08:35:40AM +0900, Daniel Castro wrote:
>> Hello All,
>>
>> I have a little setback with the development of PV Drivers for Xen in 
>> SeaBIOS.
>
> Hey, seems I read your emails out of sync.
>
>> The initialization code that runs in 32 Bit is working properly.
>> But, when the system tries to read on the disk I use the ring macros
>> to get a request. The macro usage looks like this:
>> struct blkif_ring * shared = memalign_low(4096,4096); //return
>> 0x000fd630 this above 16bit address space
>> SHARED_RING_INIT(shared);
>> So far I have a pointer located at 0x0009a000
>> Under 32bit the struct is correct and all is working according to plan.
>>
>> But on 16bit operation read on disk I have
>> struct blkfront_info * shared_ring =
>> container_of(op->drive_g.info->shared)); // I get d630 I should get it
>> from the correct segment, but how?
>> RING_GET_REQUEST(shared_ring); //this returns 0xffff and should be
>> something 0xa010 segment SS or something like that
>>
>> SeaBios has some macros that convert a pointer in 32Bit to 16Bit by
>> changing the segment register, yet I do not know in what segment the
>> ring is located, and the macros are not applied inside the procedure
>> of the macro, for example:
>
> There should be some way to set your physical address (so
> 9a000) to a segment?
>
>> MAKE_FLATPTR(GET_SEG(SS),RING_GET_REQUEST(shared_ring));
>> But this will change a 16Bit pointer of segment SS to a 32 bit
>> segment. There is also the reverse but, again I do not know the
>> segment in which I should look for. Lastly the process inside the
>> macro does not get this benefin, and I do not know if the macro will
>> work with a pointer of size 16bits.
>
> 16-bits should be fine. The problem is if you run your pointer
> outside the 16-bit segment.
Thanks for the response Konrad, Seabios provides some macross that
will set the segment automatically, you only need to use a specific
malloc to get the memory; For example:
int * pointer VAR16VISIBLE;
pointer = mallow_low(sizeof(pointer));
This code will create the pointer in a specific segment, so later when I use:
printf("%p",GET_GLOBALFLAT(pointer)); This will return the 32bit
address of it, If I do not use the GET_GLOBAL macro I will only get
the offset on the segment.
>
>>
>> Any help will be GREATLY appreciated, I am almost done.
>>
>> Thanks,
>>
>> Daniel
>> --
>> +-=====---------------------------+
>> | +---------------------------------+ | This space intentionally blank
>> for notetaking.
>> | |   | Daniel Castro,                |
>> | |   | Consultant/Programmer.|
>> | |   | U Andes                         |
>> +-------------------------------------+
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel



-- 
+-=====---------------------------+
| +---------------------------------+ | This space intentionally blank
for notetaking.
| |   | Daniel Castro,                |
| |   | Consultant/Programmer.|
| |   | U Andes                         |
+-------------------------------------+

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