ABI updates
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- v1 Latest4 patches 0 repliesNew
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 4/4 | ARM: hwcap: disable HWCAP_SWP if the CPU advertises it has exclusives | +0 | 1 reply | |
| 4/4 | ARM: hwcap: disable HWCAP_SWP if the CPU advertises it has exclusives | +0 | 1 reply | |
| 4/4 | ARM: hwcap: disable HWCAP_SWP if the CPU advertises it has exclusives | +0 | 1 reply | |
| 4/4 | ARM: hwcap: disable HWCAP_SWP if the CPU advertises it has exclusives | +0 | 1 reply | |
| 4/4 | ARM: hwcap: disable HWCAP_SWP if the CPU advertises it has exclusives | +0 | 0 replies |
Reviews trailers per patch
All 5 patches have a Reviewed-by or Acked-by.
| Patch | Catalin Marinas |
|---|---|
| 4/4 | A-b |
| 4/4 | A-b |
| 4/4 | A-b |
| 4/4 | A-b |
| 4/4 | A-b |
Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes.
Cover letter [PATCH 0/4] ABI updates
Quoted 16 lines · Russell King - ARM Linux
As a result of the recent discussions about android, several issues have been identified with existing kernels:
1.
HWCAP_SWPdoes not properly reflect whether the SWP instruction should be used. TurnHWCAP_SWPoff on ARMv6+ where the exclusives are available.2. SWP is unsafe when running on a SMP CPU; there is no bus locking between the read and write parts of the instruction execution. Force SWP emulation on ARMv7+ where we can disable the SWP instruction.
3. Reporting of alignment faults - kernel mode faults are silent due to the requirements of the network stack, but we can note where the last one occurs.
Quoted 6 lines
Testing reveals that at least my OMAP4430 userspace (supplied from TI) executes lots of SWP instructions, which is something that wasn't known before this patch.
Many systems today are not configured with SWP emulation enabled on SMP. This means that the SWP instruction is available, but unsafe.
The patches look fine to me (we are still discussing patch 4 but even if it needs changing for TLS, it can be done separately from this series).
Question - should we go a step further and change the pr_debug() in swp_emulate.c to something like pr_warn()?
Another deprecated feature is CP15 barriers (disable bit coming with the virtualisation extensions). I think we should start emulating these soon as well and print warnings.
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Catalin