Re: [PATCHv3 7/8] x86: Expose untagging mask in /proc/$PID/arch_status

Kirill A. Shutemov
2022-06-11T01:28:36Z

On Fri, Jun 10, 2022 at 08:24:38AM -0700, Dave Hansen wrote:
> On 6/10/22 07:35, Kirill A. Shutemov wrote:
> > +/*
> > + * Report architecture specific information
> > + */
> > +int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
> > + struct pid *pid, struct task_struct *task)
> > +{
> > + /*
> > + * Report AVX512 state if the processor and build option supported.
> > + */
> > + if (cpu_feature_enabled(X86_FEATURE_AVX512F))
> > + avx512_status(m, task);
> > +
> > + seq_printf(m, "untag_mask:\t%#lx\n", mm_untag_mask(task->mm));
> > +
> > + return 0;
> > +}
>
> Arch-specific gunk is great for, well, arch-specific stuff. AVX-512 and
> its, um, "quirks", really won't show up anywhere else. But x86 isn't
> even the first to be doing this address tagging business.
>
> Shouldn't we be talking to the ARM folks about a common way to do this?

+ Catalin, Will.

I guess we can expose the mask via proc for ARM too, but I'm not sure if
we can unify interface further without breaking existing TBI users: TBI is
enabled per-thread while LAM is per-process.

Any opinions?

--
Kirill A. Shutemov