[PATCH v2] ARM: advertise availability of v8 Crypto instructions

[Ard Biesheuvel]

On 10 March 2015 at 11:15, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Mon, Mar 09, 2015 at 07:38:01PM +0100, Ard Biesheuvel wrote:
>> Replying to self: looking at the arm64 code, it seems the 4-bit block
>> are signed quantities, and the negative valiues are reserved.
>> This means only signed higher values should be considered incremental,
>> and values with bit 4 set should be ignored.
>
> ITYM bit 3.
>

Sorry, yes, the top bit.

> On 32-bit, we've assumed that they're unsigned:
>
>         /* LPAE implies atomic ldrd/strd instructions */
>         vmsa = (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xf) >> 0;
>         if (vmsa >= 5)
>                 elf_hwcap |= HWCAP_LPAE;
>
>         sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
>                     ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
>         if (sync_prim >= 0x13)
>                 elf_hwcap &= ~HWCAP_SWP;
>