linux-kernel - Re: [PATCHv3 7/8] x86: Expose untagging mask in /proc/$PID/arch

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Message-ID: <144af1ab-1e7e-b75c-331c-d9c2e55b9062@intel.com>
Date:   Fri, 10 Jun 2022 08:24:38 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, Kostya Serebryany <kcc@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "H . J . Lu" <hjl.tools@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 7/8] x86: Expose untagging mask in
 /proc/$PID/arch_status

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?