On 10/02/2011 12:25 PM, Michael S. Tsirkin wrote:
On Mon, Sep 05, 2011 at 02:34:56PM +1000, David Gibson wrote:
> This patch adds functions to pci.[ch] to perform PCI DMA operations. At
> present, these are just stubs which perform directly cpu physical memory
> accesses.
>
> Using these stubs, however, distinguishes PCI device DMA transactions from
> other accesses to physical memory, which will allow PCI IOMMU support to
> be added in one place, rather than updating every PCI driver at that time.
>
> That is, it allows us to update individual PCI drivers to support an IOMMU
> without having yet determined the details of how the IOMMU emulation will
> operate. This will let us remove the most bitrot-sensitive part of an
> IOMMU patch in advance.
>
> Signed-off-by: David Gibson<da...@gibson.dropbear.id.au>
So something I just thought about:
all wrappers now go through cpu_physical_memory_rw.
This is a problem as e.g. virtio assumes that
accesses such as stw are atomic. cpu_physical_memory_rw
is a memcpy which makes no such guarantees.
Let's change cpu_physical_memory_rw() to provide that guarantee for
aligned two and four byte accesses. Having separate paths just for that
is not maintainable.
--
error compiling committee.c: too many arguments to function
