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Subject: Re: [PATCHv3 09/17] x86/mm: Implement page_keyid() using page_ext
References: <20180612143915.68065-1-kirill.shutemov@linux.intel.com>
 <20180612143915.68065-10-kirill.shutemov@linux.intel.com>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <169af1d8-7fb6-5e1a-4f34-0150570018cc@intel.com>
Date: Wed, 13 Jun 2018 11:20:10 -0700
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Sender: owner-linux-mm@kvack.org
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Ingo Molnar <mingo@redhat.com>, x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>, Tom Lendacky <thomas.lendacky@amd.com>
Cc: Kai Huang <kai.huang@linux.intel.com>, Jacob Pan <jacob.jun.pan@linux.intel.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

> +int page_keyid(const struct page *page)
> +{
> +	if (mktme_status != MKTME_ENABLED)
> +		return 0;
> +
> +	return lookup_page_ext(page)->keyid;
> +}
> +EXPORT_SYMBOL(page_keyid);

Please start using a proper X86_FEATURE_* flag for this.  It will give
you all the fancy static patching that you are missing by doing it this way.