Pass the fault type to the pager getpages routine

[markj]

Summary

This is based on some modifications in the freebsd-base-graphics tree,
which updates the in-kernel DRM module, enabling the use of a newer
libdrm and driver support for several newer generations of Intel
graphics chipsets.

The change adds a "prot" parameter to both the getpages and
getpages_async routines. By default, callers specify VM_PROT_ALL, but
vm_fault_hold() is modified to pass the true fault type, providing more
information to the fault handler. The i915 GEM fault handler uses this
hint to optimize the handler and to maintain a dirty state bit on DRM
objects.

Test Plan

I've been running with this patch on an Ivy Bridge laptop for several days.

[kib]

See D6620, esp. the discussion. Currently the new interface for GEM/TTM pages is being developed which solves both prot issue, and the prefaulting issue.

[markj]

In D8466#176055, @kib wrote:

See D6620, esp. the discussion. Currently the new interface for GEM/TTM pages is being developed which solves both prot issue, and the prefaulting issue.

Hm, ok. I remember that discussion but haven't seen any recent developments in the branch.

[alc]

In D8466#176057, @markj wrote:

In D8466#176055, @kib wrote:

See D6620, esp. the discussion. Currently the new interface for GEM/TTM pages is being developed which solves both prot issue, and the prefaulting issue.

Hm, ok. I remember that discussion but haven't seen any recent developments in the branch.

After you and I got done with the PQ_LAUNDRY work, I started talking to Kostik about this again. Essentially, we're looking to add an optional "fault handler" method to the object.

[kib]

In D8466#176057, @markj wrote:

In D8466#176055, @kib wrote:

See D6620, esp. the discussion. Currently the new interface for GEM/TTM pages is being developed which solves both prot issue, and the prefaulting issue.

Hm, ok. I remember that discussion but haven't seen any recent developments in the branch.

Which branch ? vm_pager_onfault() lives there https://kib.kiev.ua/git/gitweb.cgi?p=deviant2.git;a=shortlog;h=refs/heads/kms_iic

[markj]

In D8466#176059, @alc wrote:

After you and I got done with the PQ_LAUNDRY work, I started talking to Kostik about this again. Essentially, we're looking to add an optional "fault handler" method to the object.

Ah, got it.

In D8466#176060, @kib wrote:

Which branch ? vm_pager_onfault() lives there https://kib.kiev.ua/git/gitweb.cgi?p=deviant2.git;a=shortlog;h=refs/heads/kms_iic

I was referring to https://github.com/FreeBSDDesktop/freebsd-base-graphics and just wanted to try and push parts of it along, having spent some time reading and testing the code. But if you have a different approach planned, I'll drop this.