[PATCH 11/14] ARM: v6k: use CPU domain feature if we include support for arch < ARMv6K

Catalin Marinas catalin.marinas at arm.com
Fri Jan 28 05:46:51 EST 2011

On Fri, 2011-01-28 at 09:59 +0000, Russell King - ARM Linux wrote:
> On Fri, Jan 28, 2011 at 09:46:06AM +0000, Catalin Marinas wrote:
> > My point is that we may want SWP_EMULATE disabled (or depending on !
> > CPU_USE_DOMAINS). With domains enabled every read-only user page is
> > writeable by the kernel. This has the side-effect that SWP emulation
> > using LDREX/STREX breaks COW.
> Yes, and maybe we should instead just enable the SWP instruction by default
> on ARMv7, and if SWP emulation is built, disable it at that point.

We can't disable the SWP instruction as long as domains are enabled (COW
not working for in-kernel STREX).

On ARMv7 we could always force R/O kernel/user pages in set_pte_ext
independent of the domains setting and have early_trap_init() use
vectors_page() if cpu_architecture() >= 7 (this would actually catch
ARM11MPCore as well because of the way we interpret CPUID).


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