On 18/12/15 17:46, Mark Rutland wrote:
On Fri, Dec 18, 2015 at 05:03:11PM +0000, Suzuki K. Poulose wrote:
On 18/12/15 16:00, Yury Norov wrote:
Kernel option COMPAT defines the ability of executing aarch32 binaries.
As per ARM ARM, AArch32 only ID register values are unknown if AArch32 is
not implemented. So I think we need to skip accessing the AArch32 ID registers
everywhere (feature tracking), if the CPU doesn't supports it, to avoid
unnecessary SANITY failures and TAINTing the kernel.
That all sounds good to me.
After boot-time we should also fail hotplug of a CPU that doesn't
support AArch32, if we decided at boot-time that AArch32 was supported
accross the system. That should probably be added to your early cpu
feature verification [1].
You are right. I think we could add this as system capability to arm64_feautres
which would make the check automatic. Also, the compat_elf_arch() check won't
have to always to read_system_reg(), something like ARM64_HAS_32BIT_EL0.
Thanks
Suzuki
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