From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 1CF116B0008 for ; Mon, 18 Jun 2018 06:18:32 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id p29-v6so8449875pfi.19 for ; Mon, 18 Jun 2018 03:18:32 -0700 (PDT) Received: from mga17.intel.com (mga17.intel.com. [192.55.52.151]) by mx.google.com with ESMTPS id v10-v6si13824667plo.326.2018.06.18.03.18.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Jun 2018 03:18:30 -0700 (PDT) Date: Mon, 18 Jun 2018 13:18:28 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCHv3 10/17] x86/mm: Implement prep_encrypted_page() and arch_free_page() Message-ID: <20180618101828.hxp2dw3fmfxwk2ka@black.fi.intel.com> References: <20180612143915.68065-1-kirill.shutemov@linux.intel.com> <20180612143915.68065-11-kirill.shutemov@linux.intel.com> <36997c9c-73c0-1d9d-6251-10315a4158f0@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <36997c9c-73c0-1d9d-6251-10315a4158f0@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Ingo Molnar , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" , Tom Lendacky , Kai Huang , Jacob Pan , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, Jun 13, 2018 at 06:26:10PM +0000, Dave Hansen wrote: > On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote: > > prep_encrypted_page() also takes care about zeroing the page. We have to > > do this after KeyID is set for the page. > > This is an implementation detail that has gone unmentioned until now but > has impacted at least half a dozen locations in previous patches. Can > you rectify that, please? It was mentioned in commit message of 04/17. > > +void prep_encrypted_page(struct page *page, int order, int keyid, bool zero) > > +{ > > + int i; > > + > > + /* > > + * The hardware/CPU does not enforce coherency between mappings of the > > + * same physical page with different KeyIDs or encrypt ion keys. > > What are "encrypt ion"s? :) :P > > + * We are responsible for cache management. > > + * > > + * We flush cache before allocating encrypted page > > + */ > > + clflush_cache_range(page_address(page), PAGE_SIZE << order); > > + > > + for (i = 0; i < (1 << order); i++) { > > + WARN_ON_ONCE(lookup_page_ext(page)->keyid); > > /* All pages coming out of the allocator should have KeyID 0 */ > Okay. > > + lookup_page_ext(page)->keyid = keyid; > > + /* Clear the page after the KeyID is set. */ > > + if (zero) > > + clear_highpage(page); > > + } > > +} > > How expensive is this? It just shifts cost of zeroing from page allocator here. It should not have huge effect. > > +void arch_free_page(struct page *page, int order) > > +{ > > + int i; > > > > /* KeyId-0 pages were not used for MKTME and need no work */ > > ... or something Okay. > > + if (!page_keyid(page)) > > + return; > > Is page_keyid() optimized so that all this goes away automatically when > MKTME is compiled out or unsupported? If MKTME is not enabled compile-time, this translation unit doesn't compile at all. I have not yet optimized for run-time unsupported case. I'll optimized it based on performance measurements. > > + for (i = 0; i < (1 << order); i++) { > > + WARN_ON_ONCE(lookup_page_ext(page)->keyid > mktme_nr_keyids); > > + lookup_page_ext(page)->keyid = 0; > > + } > > + > > + clflush_cache_range(page_address(page), PAGE_SIZE << order); > > +} > > > > -- Kirill A. Shutemov