Move device memory to a weaker type. The new device memory type allows
the system to acknowledge a write to a device before the write has
completed. This is inline with VM_MEMATTR_DEVICE on armv6/armv7.
Sponsored by: Arm Ltd
Details
Details
- Reviewers
manu - Group Reviewers
arm64 - Commits
- rG3473f2832284: Switch the arm64 VM_MEMATTR_DEVICE to nGnRE
Diff Detail
Diff Detail
- Repository
- rG FreeBSD src repository
- Lint
Lint Not Applicable - Unit
Tests Not Applicable
Event Timeline
Comment Actions
Seems legit, but I never can keep all the memory models of arm in my head for more than a minute...
| sys/arm64/include/vm.h | ||
|---|---|---|
| 38–39 | You've changed it, so maybe a comment touchup is in order. | |
Comment Actions
nGnR means the hardware won't merge or reorder memory accesses. nE means it won't acknowledge a write until the device does so, switching to E relaxes this to allow this acknowledgement to happen earlier. Care needs to be taken if we need to check a write has completed but this should be mostly handled as it's also the case on armv6/armv7.