RFC arm64: change PoC D-cache flush to PoU
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b4 am 20151214151117.GD22038@mbpVersions newest first
- v1 RFC Latest1 of 2 patches 0 repliesNew
1 of 2 patches is in this archive. The cover letter announces 2.
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/2 | arm64: Defer dcache flush in __cpu_copy_user_page | +0 | 0 replies |
Reviews trailers per patch
The patch has a Reviewed-by or Acked-by.
| Patch | Catalin Marinas |
|---|---|
| 1/2 | A-b |
Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes.
Cover letter [RFC PATCH 0/2] arm64: change PoC D-cache flush to PoU
Quoted 4 lines · Ashok Kumar
Also deferred dcache flush in
__cpu_copy_user_pageto__sync_icache_dcache. May I know why I/D sync is needed in__cpu_copy_user_page? My understanding is that any self modifying code in userspace is supposed to take care of the coherency using the respective cache flush system call.
I think it may have been there for historical reasons on arch/arm (115b22474eb1 - "ARM: 5794/1: Flush the D-cache during copy_user_highpage()") and imported in arch/arm64. But looking back at this, I don't think we need it for two reasons: dynamic linker no longer relocating symbols in a text page (and cause CoW) and set_pte_at() already calling __sync_icache_dcache().
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Catalin