Enable largepage support for arm64.
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Authored by markj on Sep 17 2020, 4:35 PM.

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Reviewers

manu
alc
kib

Group Reviewers

arm64

Commits

rS366090: Add a vmparam.h constant indicating pmap support for large pages.

Summary

Use a vmparam.h constant to indicate support for non-transparent largepage mappings. Use it in the shm code.
Enable on arm64.

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Buildable 33610
Build 30856: arc lint + arc unit

Event Timeline

markj created this revision.Sep 17 2020, 4:35 PM

Herald added a reviewer: manu. · View Herald TranscriptSep 17 2020, 4:35 PM

Herald added subscribers: jhibbits, emaste, andrew. · View Herald Transcript

markj requested review of this revision.Sep 17 2020, 4:35 PM

Harbormaster completed remote builds in B33610: Diff 77143.Sep 17 2020, 4:35 PM

markj added reviewers: alc, kib, arm64.Sep 17 2020, 4:38 PM

I did not do it this way because my feel was that requires asserts in other pmap_enter() that PMAP_ENTER_LARGEPAGE is not set. It might be fine as is.

In D26467#589425, @kib wrote:

I did not do it this way because my feel was that requires asserts in other pmap_enter() that PMAP_ENTER_LARGEPAGE is not set. It might be fine as is.

Why does the current scheme not require such assertions? I don't mind adding them to this diff, or simply extending the ifdef in kern_shm_open2(). I just prefer having a central place to indicate PMAP_ENTER_LARGEPAGE support.

In D26467#589636, @markj wrote:

In D26467#589425, @kib wrote:

I did not do it this way because my feel was that requires asserts in other pmap_enter() that PMAP_ENTER_LARGEPAGE is not set. It might be fine as is.

Why does the current scheme not require such assertions? I don't mind adding them to this diff, or simply extending the ifdef in kern_shm_open2(). I just prefer having a central place to indicate PMAP_ENTER_LARGEPAGE support.

I am not advocating keeping the current scheme, but for me its advantage was that there is simple place where the support for LARGEPAGE is specified per-arch. With PMAP_HAS_LARGEPAGE I need to inspect all <arch>/include/vmparam.h.

If switching to this scheme, we should provide a pattern for pmap_enter() where somebody copying current implementation to a new architecture clearly see that the flag is handled or not. My scheme makes it correct without any action from the porter.

In D26467#589671, @kib wrote:

In D26467#589636, @markj wrote:

In D26467#589425, @kib wrote:

I did not do it this way because my feel was that requires asserts in other pmap_enter() that PMAP_ENTER_LARGEPAGE is not set. It might be fine as is.

Why does the current scheme not require such assertions? I don't mind adding them to this diff, or simply extending the ifdef in kern_shm_open2(). I just prefer having a central place to indicate PMAP_ENTER_LARGEPAGE support.

I am not advocating keeping the current scheme, but for me its advantage was that there is simple place where the support for LARGEPAGE is specified per-arch. With PMAP_HAS_LARGEPAGE I need to inspect all <arch>/include/vmparam.h.

If switching to this scheme, we should provide a pattern for pmap_enter() where somebody copying current implementation to a new architecture clearly see that the flag is handled or not. My scheme makes it correct without any action from the porter.

How about we just assert PMAP_HAS_LARGEPAGES == 1 in the bdry_idx != 0 case in vm_fault_populate()? Then, if a porter defines a new arch without PMAP_ENTER_LARGEPAGE support but defines PMAP_HAS_LARGEPAGES == 1, it will be easily found by regression tests.

In D26467#590295, @markj wrote:

How about we just assert PMAP_HAS_LARGEPAGES == 1 in the bdry_idx != 0 case in vm_fault_populate()? Then, if a porter defines a new arch without PMAP_ENTER_LARGEPAGE support but defines PMAP_HAS_LARGEPAGES == 1, it will be easily found by regression tests.

Fine with me.