drm/nouveau/mmu/gp100-: support vmms with gcc/tex replayable faults enabled

Some GPU units are capable of supporting "replayable" page faults, where
the execution unit will wait for SW to fixup GPU page tables rather than
triggering a channel-fatal fault.

This feature isn't useful (it's harmful, even) unless something like HMM
is being used to manage events appearing in the replayable fault buffer,
so, it's disabled by default.

This commit allows a client to request it be enabled.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/mmu/gp100-: add privileged methods for fault replay/cancel

Host methods exist to do at least some of what we need, but we are not
currently pushing replay/cancels through a channel like UVM does as it's
not clear whether it's necessary in our case (UVM also updates PTEs with
the GPU).

UVM also pushes a software method for fault cancels on Pascal, seemingly
because the host methods don't appear to be sufficient. If/when we want
to push the replay/cancel on the GPU, we can re-purpose the cancellation
code here to implement that swmthd.

Keep it simple for now, until we figure out exactly what we need here.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/mmu/gp100,gp10b: implement new vmm backend

Adds support for:
- 64KiB/2MiB big page sizes (128KiB not supported by HW with new PT layout).
- System-memory PTs.
- LPTE "invalid" state.
- (Tegra) Use of video memory aperture.
- Sparse PDEs/PTEs.
- Additional blocklinear kinds.
- 49-bit address-space.

GP100 supports an entirely new 5-level page table layout that provides
an expanded 49-bit address-space. It also supports the layout present
on previous generations, which we've been making do with until now.

This commit implements support for the new layout, and enables it by
default.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/mmu/gp100,gp10b: implement vmm on top of new base

Adds support for:
- Selection of old/new-style page table layout (GP100MmuLayout=0/1).
- System-memory PDs.

New layout disabled by default for the moment, as we don't have a
backend that can handle it yet.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>