From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 2A63D6B0007 for ; Thu, 29 Mar 2018 08:44:16 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id p2so2729767wre.19 for ; Thu, 29 Mar 2018 05:44:16 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id y43sor3527000ede.20.2018.03.29.05.44.14 for (Google Transport Security); Thu, 29 Mar 2018 05:44:15 -0700 (PDT) Date: Thu, 29 Mar 2018 15:43:38 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCHv2 12/14] x86/mm: Implement page_keyid() using page_ext Message-ID: <20180329124338.vxzjpkz3ecyor5uc@node.shutemov.name> References: <20180328165540.648-1-kirill.shutemov@linux.intel.com> <20180328165540.648-13-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: "Kirill A. Shutemov" , Ingo Molnar , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" , Tom Lendacky , Kai Huang , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, Mar 28, 2018 at 09:59:23AM -0700, Dave Hansen wrote: > On 03/28/2018 09:55 AM, Kirill A. Shutemov wrote: > > +static inline int page_keyid(struct page *page) > > +{ > > + if (!mktme_nr_keyids) > > + return 0; > > + > > + return lookup_page_ext(page)->keyid; > > +} > > This doesn't look very optimized. Don't we normally try to use > X86_FEATURE_* for these checks so that we get the runtime patching *and* > compile-time optimizations? I didn't go to micro optimization just yet. I would like to see whole stack functioning first. It doesn't make sense to use cpu_feature_enabledX86_FEATURE_TME) as it would produce false-positives: MKTME enumeration requires MSR read. We may change mktme_nr_keyids check to a static key here. But this is not urgent. -- Kirill A. Shutemov