Florian Weimer <fwei...@redhat.com> writes:
> On 10/12/2017 12:17 PM, Michael Ellerman wrote:
>> + pr_info("Enabling TM (Transactional Memory) with Suspend Disabled\n");
>> + cur_cpu_spec->cpu_features |= CPU_FTR_TM;
>> + cur_cpu_spec->cpu_user_features2 |= PPC_FEATURE2_HTM_NO_SUSPEND;
>> + tm_suspend_disabled = true;
>
> This doesn't look right because if suspend is not available, you need to
> clear the original PPC_FEATURE2_HTM flag because the semantics are not
> right, so that applications can use fallback code.
Yes I agree, but the PPC_FEATURE2_HTM bit is already clear. I've updated
the patch to clear it explicitly, see my other mail.
> Otherwise,
> applications may incorrectly select the HTM code and break if running on
> a system which supports HTM, but without the suspend state.
Yes.
> The new flag should say that HTM is supported, but without the suspend
> state, and it should be always set if PPC_FEATURE2_HTM is set.
I don't agree with that. HTM and HTM_NO_SUSPEND are mutually exclusive.
I don't understand how it would work if HTM_NO_SUSPEND was "always set
if PPC_FEATURE2_HTM is set"? That would tell apps that HTM with suspend
is supported and HTM without suspend is supported, which is meaningless
AFAICS.
cheers
