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[Qemu-devel] Re: PATCH/RFC: PCI memory mapping

From: Tristan Gingold
Subject: [Qemu-devel] Re: PATCH/RFC: PCI memory mapping
Date: Thu, 2 Apr 2009 17:18:43 +0200

On Apr 2, 2009, at 4:57 PM, Brian Wheeler wrote:

[first off, if there's an easier way to do this, let me know!]

This patch adds an address mapping function to the PCI bus so the host
chipset can remap PCI generated addresses to the appropriate physical

I have been thinking about this for a while as many 64bits machines have an IOTLB or IOMMU.
And with VTd and AMD IOMMU it is becoming common.

It adds two parameters to pci_register_bus:

PCIBus *pci_register_bus(pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
                        qemu_irq *pic, int devfn_min, int nirq,
                         pci_map_addr_fn map_addr, void *map_addr_opaque)

map_addr_opaque should be simply opaque (in case of new callbacks are added).

The map_addr is a function which has the prototype:

typedef target_phys_addr_t (*pci_map_addr_fn)(void *opaque, int bus_num,
                                              target_phys_addr_t addr);

I think this is not complete enough.

I'd replace int bus_num with PCIDevice *dev. You can get the pci bus from the device.
The IOTLB mapping may depend on the device so we really need it.

Second you need to pass and return a length as the mapping is valid only for a certain length.

In the future the returned length could be 0 to simulate a pci abort...

and the map_addr_opaque data is a pointer to the IOTLB buffer in the

When a pci device is doing dma or needs to write to the system, it can
use the

target_phys_addr_t pci_phys_addr(PCIDevice *device,
                                 target_phys_addr_t addr);

function to get the mapped target address.

If map_addr is NULL the function just returns the address it was passed. Otherwise the map_addr function is called and the address is translated.

I think we should do this in new functions such as pci_memory_read/ pci_memory_write which will
replace cpu_physical_memory_read/cpu_physical_memory_write.

Thank you for working on this,

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