Re: [RFCv2 00/10] Linear Address Masking enabling

Thomas Gleixner
2022-05-13T08:28:42Z

On Thu, May 12 2022 at 20:05, Dave Hansen wrote:

> On 5/12/22 18:27, Thomas Gleixner wrote:
>> On Thu, May 12 2022 at 17:46, Dave Hansen wrote:
>>> On 5/12/22 17:08, H.J. Lu wrote:
>>> If I had to take a shot at this today, I think I'd opt for:
>>>
>>> mask = sys_enable_masking(bits=6, flags=FUZZY_NR_BITS);
>>>
>>> although I'm not super confident about the "fuzzy" flag. I also don't
>>> think I'd totally hate the "blind" interface where the kernel just gets
>>> to pick unilaterally and takes zero input from userspace.
>> That's the only sane choice and you can make it simple for userspace:
>>
>> ret = prctl(GET_XXX_MASK, &mask);
>>
>> and then let it decide based on @ret and @mask whether to use it or not.
>>
>> But of course nobody thought about this as a generic feature and so we
>> have the ARM64 TBI muck as a precedence.
>
> Well, not quite *nobody*:
>
> https://lore.kernel.org/linux-arm-kernel/7a34470c-73f0-26ac-e63d-161191d4b1e4@intel.com/

Sigh....