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Re: [Qemu-devel] [RFC] QOMification of AXI stream
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] [RFC] QOMification of AXI stream |
Date: |
Tue, 12 Jun 2012 16:48:39 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 |
On 06/12/2012 04:32 PM, Peter Maydell wrote:
> On 12 June 2012 14:18, Avi Kivity <address@hidden> wrote:
>> On 06/12/2012 03:58 PM, Peter Maydell wrote:
>>> On 11 June 2012 18:31, Avi Kivity <address@hidden> wrote:
>>>> On 06/11/2012 06:01 PM, Anthony Liguori wrote:
>>>>> Perhaps we should just make MemoryRegion work in both directions?
>>>
>>>> The other direction is currently cpu_physical_memory_rw(). We do need
>>>> to support issuing transactions from arbitrary points in the memory
>>>> hierarchy, but I don't think a device's MemoryRegion is the right
>>>> interface. Being able to respond to memory transactions, and being able
>>>> to issue them are two different things.
>>>
>>> ...they're just opposite sides of the same interface, though,
>>> really. For instance you could say that any memory transaction
>>> master (cpu, dma controller, whatever) should take a single
>>> MemoryRegion* and must issue all its memory accesses to that MR*.
>>> (obviously that would usually be a container region.)
>>
>> It would be a container region, and it would be unrelated to any other
>> regions held by the device (the device might not have any memory
>> regions; instead it would only be able to do dma).
>
> It shouldn't actually be owned by the transaction master, but
> by whatever the parent object is that created the transaction
> master. So for instance for an ARM board you'd have something
> like:
> * top level machine QOM object creates a 'system-memory'
> container region, and puts all the devices in it in their
> correct locations
> * top level object also creates the cortex-a9 device, and
> passes it a pointer to the system-memory container
> * the cortex-a9 device instantiates the CPU cores and the
> per-cpu devices, and creates a container region for
> each cpu containing (devices for that cpu, plus the
> system-memory region it got passed). It passes a pointer
> to the right region to each cpu core
> * the cpu cores just use the region they're given
> * if there's a dma controller in the system, the top level
> machine object creates the controller and hands it a
> pointer to the system-memory container region too. (So
> the dma controller correctly doesn't see the per-cpu
> devices.)
>
> (when I say 'passes a pointer' I mean something involving
> QOM links I expect. I'm not sure if anybody's thought about
> how we expose memory regions in a QOM manner.)
>
> Notice that in this approach it's perfectly valid to have
> a board model which creates a single device and a single
> CPU and passes the device's MemoryRegion directly to the
> CPU. This corresponds to a hardware design where the CPU's
> address lines just connect straight to the device's, ie
> there's no bus fabric or address decoding.
Yes, exactly.
If the devices sees a byte-swapping bus, then instead of giving it a
container region, we give it an io region; the callbacks byte-swap and
write the contents to a container that does the rest of the forwarding.
If it's an address remapping iommu, then we pass it a container region
with an alias-per-page that remaps the device addresses to addresses in
another container:
iommu
|
+-alias-page-0 ---> system_memory[7]
|-alias-page-1 ---> system_memory[3]
.
.
.
So a device write to page 1 is redirected to page 3. Of course in both
cases we'll want to fold the functionality into the memory API instead
of making the iommu writer work so hard.
--
error compiling committee.c: too many arguments to function
- Re: [Qemu-devel] [RFC] QOMification of AXI streams, (continued)
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Avi Kivity, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Edgar E. Iglesias, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Anthony Liguori, 2012/06/11
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Avi Kivity, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Maydell, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Avi Kivity, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Peter Maydell, 2012/06/12
- Re: [Qemu-devel] [RFC] QOMification of AXI stream,
Avi Kivity <=
- Re: [Qemu-devel] [RFC] QOMification of AXI stream, Andreas Färber, 2012/06/12