On Wednesday 16 September 2009, Michael S. Tsirkin wrote: > On Wed, Sep 16, 2009 at 04:57:42PM +0200, Arnd Bergmann wrote: > > On Tuesday 15 September 2009, Michael S. Tsirkin wrote: > > > 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. > > > We are talking about doing this in userspace, not in kernel. Ok, that's fine then. I thought the idea was to use the vhost_net driver to access the user memory, which would be a really cute hack otherwise, as you'd only need to provide the eventfds from a hardware specific driver and could use the regular virtio_net on the other side. Arnd <>< _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
