On 19 July 2017 at 08:22, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Tue, Jul 18, 2017 at 2:21 PM, Dave Airlie <airl...@gmail.com> wrote: >> >> Oh and just FYI, the machine I've tested this on has an mgag200 server >> graphics card backing the framebuffer, but with just efifb loaded. > > Yeah, it looks like it needs special hardware - and particularly the > kind of garbage hardware that people only have on servers. > > Why do server people continually do absolute sh*t hardware? It's crap, > crap, crap across the board outside the CPU. Nasty and bad hacky stuff > that nobody else would touch with a ten-foot pole, and the "serious > enterprise" people lap it up like it was ambrosia. > > It's not just "graphics is bad anyway since we don't care". It's all > the things they ostensibly _do_ care about too, like the disk and the > fabric infrastructure. Buggy nasty crud.
I've tried to reproduce now on: Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz using some address space from 02:00.0 3D controller: NVIDIA Corporation GM108M [GeForce 940MX] (rev a2) And I don't see the issue. I'll try and track down some more efi compatible mga or other wierd server chips stuff if I can. > Anyway, rant over. I wonder if we could show this without special > hardware by just mapping some region that doesn't even have hardware > in it as WC. Do we even expose the PAT settings to user space, though, > or do we always have to have some fake module to create the PAT stuff? I do wonder wtf the hw could be doing that would cause this, but I've no idea how to tell what difference a write combined PCI transaction would have on the bus side of things, and what the device could generate that would cause such a horrible slowdown. Dave.
