On Wed, Sep 16, 2009 at 04:57:42PM +0200, Arnd Bergmann wrote:

On Tuesday 15 September 2009, Michael S. Tsirkin wrote:

quoted

Userspace in x86 maps a PCI region, uses it for communication with ppc?

This might have portability issues. On x86 it should work, but if the
host is powerpc or similar, you cannot reliably access PCI I/O memory
through copy_tofrom_user but have to use memcpy_toio/fromio or readl/writel
calls, which don't work on user pointers.

Specifically on powerpc, copy_from_user cannot access unaligned buffers
if they are on an I/O mapping.

	Arnd <><

We are talking about doing this in userspace, not in kernel.

-- 
MST

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