Kroah-Hartman: AF_BUS, D-Bus, and the Linux kernel
Posted Feb 14, 2013 6:25 UTC (Thu) by brouhaha
In reply to: Kroah-Hartman: AF_BUS, D-Bus, and the Linux kernel
Parent article: Kroah-Hartman: AF_BUS, D-Bus, and the Linux kernel
GPUs can do DMA. Allowing userspace to submit arbitrary commands to GPUs means that userspace can do arbitrary DMA, and as such means that any application with access to your GPU can do anything it wants to.
Which is why you wouldn't let just any userspace application access the GPU directly. I don't let just any userspace application scribble on /dev/sda either.
I'll accept your argument for modesetting for suspend/resume.
There's plenty that the kernel does that can't be handled in userspace, simply because (a) we don't trust userspace,
That's a bizarre argument. Having code in user space doesn't magically make it less trustworthy than the same code would be in kernel space. Whether particular code should be trusted is a matter of policy, and there are various mechanism for policy enforcement.
The only reason to push hardware management out of your kernel is because you're producing a microkernel,
Assumes facts not in evidence. At the very large router company, we pushed hardware management out of the kernel for many reasons, none of which had anything whatsoever to do with whether the kernel we were running was monolithic or a microkernel. I could certainly accept that *A* reason to push hardware management out of your kernel is because you're producing a microkernel. It's a big jump from *A* to *The only*.
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