From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51A55C433F5 for ; Wed, 8 Dec 2021 08:58:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E151C6B0074; Wed, 8 Dec 2021 03:58:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D9E406B0078; Wed, 8 Dec 2021 03:58:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C65BD6B007B; Wed, 8 Dec 2021 03:58:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay040.a.hostedemail.com [64.99.140.40]) by kanga.kvack.org (Postfix) with ESMTP id B5CAF6B0074 for ; Wed, 8 Dec 2021 03:58:47 -0500 (EST) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 8E51520747 for ; Wed, 8 Dec 2021 08:58:37 +0000 (UTC) X-FDA: 78894026274.12.56731AA Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by imf29.hostedemail.com (Postfix) with ESMTP id E8859900024B for ; Wed, 8 Dec 2021 08:58:35 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R301e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=xuyu@linux.alibaba.com;NM=1;PH=DS;RN=13;SR=0;TI=SMTPD_---0Uzrn5-M_1638953910; Received: from 30.225.28.56(mailfrom:xuyu@linux.alibaba.com fp:SMTPD_---0Uzrn5-M_1638953910) by smtp.aliyun-inc.com(127.0.0.1); Wed, 08 Dec 2021 16:58:31 +0800 Message-ID: Date: Wed, 8 Dec 2021 16:58:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH v2 07/14] x86/clear_page: add clear_page_uncached() Content-Language: en-US To: Ankur Arora , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: mingo@kernel.org, bp@alien8.de, luto@kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com, jon.grimm@amd.com, kvm@vger.kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com References: <20211020170305.376118-1-ankur.a.arora@oracle.com> <20211020170305.376118-8-ankur.a.arora@oracle.com> From: Yu Xu In-Reply-To: <20211020170305.376118-8-ankur.a.arora@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E8859900024B X-Stat-Signature: mwhpy9uiudon3jokfne159wocsdjthf7 Authentication-Results: imf29.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf29.hostedemail.com: domain of xuyu@linux.alibaba.com designates 115.124.30.43 as permitted sender) smtp.mailfrom=xuyu@linux.alibaba.com X-HE-Tag: 1638953915-639541 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/21/21 1:02 AM, Ankur Arora wrote: > Expose the low-level uncached primitives (clear_page_movnt(), > clear_page_clzero()) as alternatives via clear_page_uncached(). > Also fallback to clear_page(), if X86_FEATURE_MOVNT_SLOW is set > and the CPU does not have X86_FEATURE_CLZERO. > > Both the uncached primitives use stores which are weakly ordered > with respect to other instructions accessing the memory hierarchy. > To ensure that callers don't mix accesses to different types of > address_spaces, annotate clear_user_page_uncached(), and > clear_page_uncached() as taking __incoherent pointers as arguments. > > Also add clear_page_uncached_make_coherent() which provides the > necessary store fence to flush out the uncached regions. > > Signed-off-by: Ankur Arora > --- > > Notes: > This patch adds the fallback definitions of clear_user_page_uncached() > etc in include/linux/mm.h which is likely not the right place for it. > > I'm guessing these should be moved to include/asm-generic/page.h > (or maybe a new include/asm-generic/page_uncached.h) and for > architectures that do have arch/$arch/include/asm/page.h (which > seems like all of them), also replicate there? > > Anyway, wanted to first check if that's the way to do it, before > doing that. > > arch/x86/include/asm/page.h | 10 ++++++++++ > arch/x86/include/asm/page_32.h | 9 +++++++++ > arch/x86/include/asm/page_64.h | 32 ++++++++++++++++++++++++++++++++ > include/linux/mm.h | 14 ++++++++++++++ > 4 files changed, 65 insertions(+) > > diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h > index 94dbd51df58f..163be03ac422 100644 > --- a/arch/x86/include/asm/page_32.h > +++ b/arch/x86/include/asm/page_32.h > @@ -39,6 +39,15 @@ static inline void clear_page(void *page) > memset(page, 0, PAGE_SIZE); > } > > +static inline void clear_page_uncached(__incoherent void *page) > +{ > + clear_page((__force void *) page); > +} > + > +static inline void clear_page_uncached_make_coherent(void) > +{ > +} > + > static inline void copy_page(void *to, void *from) > { > memcpy(to, from, PAGE_SIZE); > diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h > index 3c53f8ef8818..d7946047c70f 100644 > --- a/arch/x86/include/asm/page_64.h > +++ b/arch/x86/include/asm/page_64.h > @@ -56,6 +56,38 @@ static inline void clear_page(void *page) > : "cc", "memory", "rax", "rcx"); > } > > +/* > + * clear_page_uncached: only allowed on __incoherent memory regions. > + */ > +static inline void clear_page_uncached(__incoherent void *page) > +{ > + alternative_call_2(clear_page_movnt, > + clear_page, X86_FEATURE_MOVNT_SLOW, > + clear_page_clzero, X86_FEATURE_CLZERO, > + "=D" (page), > + "0" (page) > + : "cc", "memory", "rax", "rcx"); > +} > + > +/* > + * clear_page_uncached_make_coherent: executes the necessary store > + * fence after which __incoherent regions can be safely accessed. > + */ > +static inline void clear_page_uncached_make_coherent(void) > +{ > + /* > + * Keep the sfence for oldinstr and clzero separate to guard against > + * the possibility that a cpu-model both has X86_FEATURE_MOVNT_SLOW > + * and X86_FEATURE_CLZERO. > + * > + * The alternatives need to be in the same order as the ones > + * in clear_page_uncached(). > + */ > + alternative_2("sfence", > + "", X86_FEATURE_MOVNT_SLOW, > + "sfence", X86_FEATURE_CLZERO); > +} > + > void copy_page(void *to, void *from); > > #ifdef CONFIG_X86_5LEVEL > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 73a52aba448f..b88069d1116c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3192,6 +3192,20 @@ static inline bool vma_is_special_huge(const struct vm_area_struct *vma) > > #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */ > > +#ifndef clear_user_page_uncached Hi Ankur Arora, I've been looking for where clear_user_page_uncached is defined in this patchset, but failed. There should be something like follows in arch/x86, right? static inline void clear_user_page_uncached(__incoherent void *page, unsigned long vaddr, struct page *pg) { clear_page_uncached(page); } Did I miss something? > +/* > + * clear_user_page_uncached: fallback to the standard clear_user_page(). > + */ > +static inline void clear_user_page_uncached(__incoherent void *page, > + unsigned long vaddr, struct page *pg) > +{ > + clear_user_page((__force void *)page, vaddr, pg); > +} > + > +static inline void clear_page_uncached_make_coherent(void) { } > +#endif > + > + > #ifdef CONFIG_DEBUG_PAGEALLOC > extern unsigned int _debug_guardpage_minorder; > DECLARE_STATIC_KEY_FALSE(_debug_guardpage_enabled); > -- Thanks, Yu