On Wed, Sep 16, 2009 at 05:22:37PM +0200, Arnd Bergmann wrote: > 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 It's a separate issue. We were talking generally about configuration and setup. Gregory implemented it in kernel, Avi wants it moved to userspace, with only fastpath in kernel. > 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 <>< To do that, maybe copy to user on ppc can be fixed, or wrapped around in a arch specific macro, so that everyone else does not have to go through abstraction layers. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
