[Qemu-devel] PCI address question

[Qemu-devel] PCI address question

[Màrius Montón]

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Hello,

For my PCI device to QEMU, I need the real address the PCI bus is using
to access my device. For a IO BAR (PCI_ADDRESS_SPACE_IO), I receive the
real address (like 0xc200 or similar), but when registering a
PCI_ADDRESS_SPACE_MEM I only receive the offset to the BAR.

How I can receive or obtaint the real address on each access to my device?

Cjeers,

Màrius

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[Qemu-devel] Re: PCI address question

[Màrius Montón]

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Màrius Montón wrote:
> Hello,
>
> For my PCI device to QEMU, I need the real address the PCI bus is using
> to access my device. For a IO BAR (PCI_ADDRESS_SPACE_IO), I receive the
> real address (like 0xc200 or similar), but when registering a
> PCI_ADDRESS_SPACE_MEM I only receive the offset to the BAR.
>
> How I can receive or obtaint the real address on each access to my device?
>
> Cjeers,
>
> Màrius
>   
nobody can tell me anything? :(

Marius

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Re: [Qemu-devel] Re: PCI address question

[Lennart Sorensen]

On Tue, Oct 27, 2009 at 04:05:25PM +0100, Màrius Montón wrote:
> Màrius Montón wrote:
> > Hello,
> >
> > For my PCI device to QEMU, I need the real address the PCI bus is using
> > to access my device. For a IO BAR (PCI_ADDRESS_SPACE_IO), I receive the
> > real address (like 0xc200 or similar), but when registering a
> > PCI_ADDRESS_SPACE_MEM I only receive the offset to the BAR.
> >
> > How I can receive or obtaint the real address on each access to my device?
> >
> > Cjeers,
> >
> > Màrius
> >   
> nobody can tell me anything? :(

Add the offset to the address in the bar?

After all the OS is allowed to change your BAR if it wants to.
So internally the only thing that makes sense to a PCI device is the
offset from it's base address.

You listen to addresses at your IO range, and at your memory BAR range.
What you do when you see a request for your range then depends on the
offset that address had from the current base.  This would also be true
for the IO.

-- 
Len Sorensen

Re: [Qemu-devel] Re: PCI address question

[Màrius Montón]

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[Qemu-devel] Re: Re: PCI address question

[Michael S. Tsirkin]

On Thu, Oct 29, 2009 at 12:30:02PM +0100, Màrius Montón wrote:
> Lennart Sorensen wrote:
> 
>     On Tue, Oct 27, 2009 at 04:05:25PM +0100, Màrius Montón wrote:
> 
> 
>         Màrius Montón wrote:
> 
> 
>             Hello,
> 
>             For my PCI device to QEMU, I need the real address the PCI bus is using
>             to access my device. For a IO BAR (PCI_ADDRESS_SPACE_IO), I receive the
>             real address (like 0xc200 or similar), but when registering a
>             PCI_ADDRESS_SPACE_MEM I only receive the offset to the BAR.
> 
>             How I can receive or obtaint the real address on each access to my device?
> 
>             Cjeers,
> 
>             Màrius
> 
> 
> 
>         nobody can tell me anything? :(
> 
> 
>     Add the offset to the address in the bar?
> 
> The problem is how to know what bar is accessing in case I have only one
> function for all BARs.

I expect that's unusual: different BARs usually have different
functionality. Just implement different functions and pass
calls on to a shared helper?

>     After all the OS is allowed to change your BAR if it wants to.
>     So internally the only thing that makes sense to a PCI device is the
>     offset from it's base address.
> 
>     You listen to addresses at your IO range, and at your memory BAR range.
>     What you do when you see a request for your range then depends on the
>     offset that address had from the current base.  This would also be true
>     for the IO.
> 
> I know all PCI internals, but I don't understand why for IO I receive all
> address and only the offset for MEM BARs (or I'm wrong?)
> 
> Màrius

PCI only calls a map method. I think this gets a 32 bit address, not BAR offset:

               r->addr = new_addr;
               if (r->addr != -1) {
                   r->map_func(d, i, r->addr, r->size, r->type);
               }


-- 
MST

[Qemu-devel] Re: PCI address question

[Màrius Montón]

Michael S. Tsirkin wrote:
> On Thu, Oct 29, 2009 at 12:30:02PM +0100, Màrius Montón wrote:
>   
>> Lennart Sorensen wrote:
>>
>>     On Tue, Oct 27, 2009 at 04:05:25PM +0100, Màrius Montón wrote:
>>
>>
>>         Màrius Montón wrote:
>>
>>
>>             Hello,
>>
>>             For my PCI device to QEMU, I need the real address the PCI bus is using
>>             to access my device. For a IO BAR (PCI_ADDRESS_SPACE_IO), I receive the
>>             real address (like 0xc200 or similar), but when registering a
>>             PCI_ADDRESS_SPACE_MEM I only receive the offset to the BAR.
>>
>>             How I can receive or obtaint the real address on each access to my device?
>>
>>             Cjeers,
>>
>>             Màrius
>>
>>
>>
>>         nobody can tell me anything? :(
>>
>>
>>     Add the offset to the address in the bar?
>>
>> The problem is how to know what bar is accessing in case I have only one
>> function for all BARs.
>>     
>
> I expect that's unusual: different BARs usually have different
> functionality. Just implement different functions and pass
> calls on to a shared helper?
>
>   
It is because I'm trying to add PCI devices from a configuration file
(no hot-plug), and this way was the easies way I found... any idea?
>>     After all the OS is allowed to change your BAR if it wants to.
>>     So internally the only thing that makes sense to a PCI device is the
>>     offset from it's base address.
>>
>>     You listen to addresses at your IO range, and at your memory BAR range.
>>     What you do when you see a request for your range then depends on the
>>     offset that address had from the current base.  This would also be true
>>     for the IO.
>>
>> I know all PCI internals, but I don't understand why for IO I receive all
>> address and only the offset for MEM BARs (or I'm wrong?)
>>
>> Màrius
>>     
>
> PCI only calls a map method. I think this gets a 32 bit address, not BAR offset:
>
>                r->addr = new_addr;
>                if (r->addr != -1) {
>                    r->map_func(d, i, r->addr, r->size, r->type);
>                }
>
>
>   
I may study that functions

Màrius