linux-kernel - Re: [PATCHv3 09/17] x86/mm: Implement page_keyid() using page

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Message-ID: <20180618100721.qvm4maovfhxbfoo7@black.fi.intel.com>
Date:   Mon, 18 Jun 2018 13:07:21 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv3 09/17] x86/mm: Implement page_keyid() using page_ext

On Wed, Jun 13, 2018 at 06:20:10PM +0000, Dave Hansen wrote:
> > +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.

There's no MKTME CPU feature.

Well, I guess we can invent syntactic one or just use static key directly.

Let's see how it behaves performance-wise before optimizing this.

-- 
 Kirill A. Shutemov