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 X-Spam-Level: X-Spam-Status: No, score=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F5FCC04FF3 for ; Mon, 24 May 2021 06:52:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BF2EB611CB for ; Mon, 24 May 2021 06:52:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF2EB611CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F035894004C; Mon, 24 May 2021 02:52:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ED9ED940042; Mon, 24 May 2021 02:52:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DA1EA94004C; Mon, 24 May 2021 02:52:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0203.hostedemail.com [216.40.44.203]) by kanga.kvack.org (Postfix) with ESMTP id A7E29940042 for ; Mon, 24 May 2021 02:52:24 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 4A4DC180ACEF3 for ; Mon, 24 May 2021 06:52:24 +0000 (UTC) X-FDA: 78175205808.01.29FA5FC Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf27.hostedemail.com (Postfix) with ESMTP id BF7678019105 for ; Mon, 24 May 2021 06:52:18 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 047E36109E; Mon, 24 May 2021 06:52:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621839142; bh=tyeI6gnQ7lQwnMRYfWYfpcezNXMnQ92WeHvEPHLHg0s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tgSJUnt+v+tNVhqKoM4KTvqfDTuMNmmizZOW99hDhjGLutvrBHvCQGh0DCB8I382h iBcjrmKJ0g+vkaVBbm19dddVEiLXwnS9NePwIlKWu8OA0p40ZSmH1ZzGniCw5BEWkz VtxwlAxVWzU8/7J4pRhfLH9+CoD6b4OL03kP0zQCFWy2FlDX0WvPprjPNzwfGfjHzt HFnJI0IKW+viKNVaPj3EjGmY6h8Bh6INgWA/OzHmAKbwSjimpAwJoh0vCskszBc7JJ 2iz3sm/dJsY7NmMGIpfJ7XYxQMdMTgHmLx/Yy6H/UTj43uJbtE9a5b+yDDV1MEsuiS GbBi4iGDYCoHA== Date: Mon, 24 May 2021 09:52:15 +0300 From: Mike Rapoport To: Anshuman Khandual Cc: linux-mm@kvack.org, david@redhat.com, akpm@linux-foundation.org, Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC V2] mm: Enable generic pfn_valid() to handle early sections with memmap holes Message-ID: References: <20210422061902.21614-1-rppt@kernel.org> <1619077823-3819-1-git-send-email-anshuman.khandual@arm.com> <10e5eecf-3ef5-f691-f38a-7ca305b707c1@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10e5eecf-3ef5-f691-f38a-7ca305b707c1@arm.com> Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=tgSJUnt+; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf27.hostedemail.com: domain of rppt@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=rppt@kernel.org X-Stat-Signature: 5t4ssh8ua6zudk1kfw1sktt7sbdeso4z X-Rspamd-Queue-Id: BF7678019105 X-Rspamd-Server: rspam02 X-HE-Tag: 1621839138-209582 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: Hello Anshuman, On Mon, May 24, 2021 at 10:28:32AM +0530, Anshuman Khandual wrote: > > On 4/22/21 1:20 PM, Anshuman Khandual wrote: > > Platforms like arm and arm64 have redefined pfn_valid() because their early > > memory sections might have contained memmap holes after freeing parts of it > > during boot, which should be skipped while validating a pfn for struct page > > backing. This scenario on certain platforms where memmap is not continuous, > > could be captured with a new option CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES. > > Then the generic pfn_valid() can be improved to accommodate such platforms. > > This reduces overall code footprint and also improves maintainability. > > > > free_unused_memmap() and pfn_to_online_page() have been updated to include > > such cases. This also exports memblock_is_memory() for all drivers that use > > pfn_valid() but lack required visibility. After the new config is in place, > > drop CONFIG_HAVE_ARCH_PFN_VALID from arm64 platforms. > > > > Cc: Catalin Marinas > > Cc: Will Deacon > > Cc: Andrew Morton > > Cc: Mike Rapoport > > Cc: David Hildenbrand > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-kernel@vger.kernel.org > > Cc: linux-mm@kvack.org > > Suggested-by: David Hildenbrand > > Signed-off-by: Anshuman Khandual > > --- > > This patch applies on the latest mainline kernel after Mike's series > > regarding arm64 based pfn_valid(). > > > > https://lore.kernel.org/linux-mm/20210422061902.21614-1-rppt@kernel.org/T/#t > > > > Changes in RFC V2: > > > > - Dropped support for arm (32 bit) > > - Replaced memblock_is_map_memory() check with memblock_is_memory() > > - MEMBLOCK_NOMAP memory are no longer skipped for pfn_valid() > > - Updated pfn_to_online_page() per David > > - Updated free_unused_memmap() to preserve existing semantics per Mike > > - Exported memblock_is_memory() instead of memblock_is_map_memory() > > > > Changes in RFC V1: > > > > - https://patchwork.kernel.org/project/linux-mm/patch/1615174073-10520-1-git-send-email-anshuman.khandual@arm.com/ > > > > arch/arm64/Kconfig | 2 +- > > arch/arm64/include/asm/page.h | 1 - > > arch/arm64/mm/init.c | 41 ----------------------------------- > > include/linux/mmzone.h | 18 ++++++++++++++- > > mm/Kconfig | 9 ++++++++ > > mm/memblock.c | 8 +++++-- > > mm/memory_hotplug.c | 5 +++++ > > 7 files changed, 38 insertions(+), 46 deletions(-) > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > index b4a9b493ce72..4cdc3570ffa9 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -144,7 +144,6 @@ config ARM64 > > select HAVE_ARCH_KGDB > > select HAVE_ARCH_MMAP_RND_BITS > > select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > > - select HAVE_ARCH_PFN_VALID > > select HAVE_ARCH_PREL32_RELOCATIONS > > select HAVE_ARCH_SECCOMP_FILTER > > select HAVE_ARCH_STACKLEAK > > @@ -167,6 +166,7 @@ config ARM64 > > if $(cc-option,-fpatchable-function-entry=2) > > select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \ > > if DYNAMIC_FTRACE_WITH_REGS > > + select HAVE_EARLY_SECTION_MEMMAP_HOLES > > select HAVE_EFFICIENT_UNALIGNED_ACCESS > > select HAVE_FAST_GUP > > select HAVE_FTRACE_MCOUNT_RECORD > > diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h > > index 75ddfe671393..fcbef3eec4b2 100644 > > --- a/arch/arm64/include/asm/page.h > > +++ b/arch/arm64/include/asm/page.h > > @@ -37,7 +37,6 @@ void copy_highpage(struct page *to, struct page *from); > > > > typedef struct page *pgtable_t; > > > > -int pfn_valid(unsigned long pfn); > > int pfn_is_map_memory(unsigned long pfn); > > > > #include > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > index f431b38d0837..5731a11550d8 100644 > > --- a/arch/arm64/mm/init.c > > +++ b/arch/arm64/mm/init.c > > @@ -217,47 +217,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > > free_area_init(max_zone_pfns); > > } > > > > -int pfn_valid(unsigned long pfn) > > -{ > > - phys_addr_t addr = PFN_PHYS(pfn); > > - > > - /* > > - * Ensure the upper PAGE_SHIFT bits are clear in the > > - * pfn. Else it might lead to false positives when > > - * some of the upper bits are set, but the lower bits > > - * match a valid pfn. > > - */ > > - if (PHYS_PFN(addr) != pfn) > > - return 0; > > - > > -#ifdef CONFIG_SPARSEMEM > > -{ > > - struct mem_section *ms; > > - > > - if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) > > - return 0; > > - > > - ms = __pfn_to_section(pfn); > > - if (!valid_section(ms)) > > - return 0; > > - > > - /* > > - * ZONE_DEVICE memory does not have the memblock entries. > > - * memblock_is_memory() check for ZONE_DEVICE based > > - * addresses will always fail. Even the normal hotplugged > > - * memory will never have MEMBLOCK_NOMAP flag set in their > > - * memblock entries. Skip memblock search for all non early > > - * memory sections covering all of hotplug memory including > > - * both normal and ZONE_DEVICE based. > > - */ > > - if (!early_section(ms)) > > - return pfn_section_valid(ms, pfn); > > -} > > -#endif > > - return memblock_is_memory(addr); > > -} > > -EXPORT_SYMBOL(pfn_valid); > > - > > int pfn_is_map_memory(unsigned long pfn) > > { > > phys_addr_t addr = PFN_PHYS(pfn); > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > > index 961f0eeefb62..18bf71665211 100644 > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -1421,10 +1421,22 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn) > > * > > * Return: 1 for PFNs that have memory map entries and 0 otherwise > > */ > > +bool memblock_is_memory(phys_addr_t addr); > > + > > static inline int pfn_valid(unsigned long pfn) > > { > > + phys_addr_t addr = PFN_PHYS(pfn); > > struct mem_section *ms; > > > > + /* > > + * Ensure the upper PAGE_SHIFT bits are clear in the > > + * pfn. Else it might lead to false positives when > > + * some of the upper bits are set, but the lower bits > > + * match a valid pfn. > > + */ > > + if (PHYS_PFN(addr) != pfn) > > + return 0; > > + > > if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) > > return 0; > > ms = __nr_to_section(pfn_to_section_nr(pfn)); > > @@ -1434,7 +1446,11 @@ static inline int pfn_valid(unsigned long pfn) > > * Traditionally early sections always returned pfn_valid() for > > * the entire section-sized span. > > */ > > - return early_section(ms) || pfn_section_valid(ms, pfn); > > + if (early_section(ms)) > > + return IS_ENABLED(CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES) ? > > + memblock_is_memory(pfn << PAGE_SHIFT) : 1; > > + > > + return pfn_section_valid(ms, pfn); > > } > > #endif > > Hello David/Mike, > > Now that pfn_is_map_memory() usage has been decoupled from pfn_valid() and > SPARSEMEM_VMEMMAP is only available memory model on arm64, wondering if we > still need this HAVE_EARLY_SECTION_MEMMAP_HOLES proposal ? Please do kindly > suggest. Thank you. Even now arm64 still frees parts of the memory map and pfn_valid() should be able to tell if a part of a section is freed or not. For instance for the following memory configuration |<----section---->|<----hole---->|<----section---->| +--------+--------+--------------+--------+--------+ | bank 0 | unused | | bank 1 | unused | +--------+--------+--------------+--------+--------+ the memory map corresponding to the "unused" areas is freed, but the generic pfn_valid() will still return 1 there. So we either should stop freeing unused memory map on arm64, or keep arm64::pfn_valid() or implement something along the lines of this patch. I personally don't think that the memory savings from freeing the unused memory map worth the pain of maintenance and bugs happening here and there. -- Sincerely yours, Mike.