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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BA67C433EF for ; Thu, 24 Feb 2022 06:27:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231303AbiBXG1p (ORCPT ); Thu, 24 Feb 2022 01:27:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231302AbiBXG1l (ORCPT ); Thu, 24 Feb 2022 01:27:41 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A24C317AB8 for ; Wed, 23 Feb 2022 22:27:11 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 541AEB8248C for ; Thu, 24 Feb 2022 06:27:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E96AC340EC; Thu, 24 Feb 2022 06:27:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645684029; bh=RfuCCY8zPmsR5Bp17+vtklf5h9j3ms7ZWNwMS/X7RF8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=L4B7jVAyolB6geCsbqCigeUDULujokT8cOt1gy4vqFaRRC794iilYUgF+U1MWtb3W 3FNYSmtBwV+EbP59MGS3VjT9oHj082T/n4S0kYaaHJFWwGQAZQ0yPgj4jY+SIwNK1k i3WnaPwzM3K1FyQ3EWcn98Y1weuI+3Hxp4AvdjBDLEtT3aRyVdPdClWIH4C+CovDE/ b3wz0eHOnA7p4R5YbceR4MOcHfrX27LDPnLI5OAX5yTssKScPBgFogi4nobrt9coPH Saj3gwOv0GJcssfcgFoHckOwiNusCDkHFHV6wivvpMv6eq9HJGPdrzlmixT9tpnuYK pd2UuDi4V65gw== Date: Thu, 24 Feb 2022 08:26:59 +0200 From: Mike Rapoport To: Vijay Balakrishna Cc: Catalin Marinas , Will Deacon , Nicolas Saenz Julienne , Anshuman Khandual , Ard Biesheuvel , Pavel Tatashin , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] arm64: Do not defer reserve_crashkernel() for platforms with no DMA memory zones Message-ID: References: <1645646253-16072-1-git-send-email-vijayb@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1645646253-16072-1-git-send-email-vijayb@linux.microsoft.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 23, 2022 at 11:57:33AM -0800, Vijay Balakrishna wrote: > The following patches resulted in deferring crash kernel reservation to > mem_init(), mainly aimed at platforms with DMA memory zones (no IOMMU), > in particular Raspberry Pi 4. > > commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32") > commit 8424ecdde7df ("arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges") > commit 0a30c53573b0 ("arm64: mm: Move reserve_crashkernel() into mem_init()") > commit 2687275a5843 ("arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation is required") > > Above changes introduced boot slowdown due to linear map creation for > all the memory banks with NO_BLOCK_MAPPINGS, see discussion[1]. The proposed > changes restore crash kernel reservation to earlier behavior thus avoids > slow boot, particularly for platforms with IOMMU (no DMA memory zones). > > Tested changes to confirm no ~150ms boot slowdown on our SoC with IOMMU > and 8GB memory. Also tested with ZONE_DMA and/or ZONE_DMA32 configs to confirm > no regression to deferring scheme of crash kernel memory reservation. > In both cases successfully collected kernel crash dump. > > [1] https://lore.kernel.org/all/9436d033-579b-55fa-9b00-6f4b661c2dd7@linux.microsoft.com/ > > Signed-off-by: Vijay Balakrishna > Cc: stable@vger.kernel.org > --- > Changes from v1 -> v2 > --------------------- > - replaced '!crashk_res.end' with IS_ENABLED(ZONE_DMA/DMA32) (Nicolas's comment) > - minor change to make it uniform -- replaced #if defined(..) -> #if IS_ENABLED(..) > - added new comment in arch/arm64/mm/init.c to ease future maintenance (Nicolas's comment) > - test performed comment moved to commit message > > [v1] https://lore.kernel.org/all/1645056294-6509-1-git-send-email-vijayb@linux.microsoft.com/ > --- > arch/arm64/mm/init.c | 36 +++++++++++++++++++++++++++++++++--- > arch/arm64/mm/mmu.c | 29 ++++++++++++++++++++++++++++- > 2 files changed, 61 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index db63cc885771..51869f9dfc33 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -61,8 +61,34 @@ EXPORT_SYMBOL(memstart_addr); > * unless restricted on specific platforms (e.g. 30-bit on Raspberry Pi 4). > * In such case, ZONE_DMA32 covers the rest of the 32-bit addressable memory, > * otherwise it is empty. > + * > + * Memory reservation for crash kernel either done early or deferred > + * depending on DMA memory zones configs (ZONE_DMA) -- > + * > + * In absence of ZONE_DMA configs arm64_dma_phys_limit initialized > + * here instead of max_zone_phys(). This lets early reservation of > + * crash kernel memory which has a dependency on arm64_dma_phys_limit. > + * Reserving memory early for crash kernel allows linear creation of block > + * mappings (greater than page-granularity) for all the memory bank rangs. > + * In this scheme a comparatively quicker boot is observed. > + * > + * If ZONE_DMA configs are defined, crash kernel memory reservation > + * is delayed until DMA zone memory range size initilazation performed in > + * zone_sizes_init(). The defer is necessary to steer clear of DMA zone > + * memory range to avoid overlap allocation. So crash kernel memory boundaries > + * are not known when mapping all bank memory ranges, which otherwise means > + * not possible to exclude crash kernel range from creating block mappings > + * so page-granularity mappings are created for the entire memory range. > + * Hence a slightly slower boot is observed. > + * > + * Note: Page-granularity mapppings are necessary for crash kernel memory > + * range for shrinking its size via /sys/kernel/kexec_crash_size interface. > */ > -phys_addr_t arm64_dma_phys_limit __ro_after_init; > +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) > +phys_addr_t __ro_after_init arm64_dma_phys_limit; > +#else > +phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; > +#endif > > #ifdef CONFIG_KEXEC_CORE > /* > @@ -153,8 +179,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > if (!arm64_dma_phys_limit) > arm64_dma_phys_limit = dma32_phys_limit; > #endif > - if (!arm64_dma_phys_limit) > - arm64_dma_phys_limit = PHYS_MASK + 1; > max_zone_pfns[ZONE_NORMAL] = max; > > free_area_init(max_zone_pfns); > @@ -315,6 +339,10 @@ void __init arm64_memblock_init(void) > > early_init_fdt_scan_reserved_mem(); > > +#if !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32) > + reserve_crashkernel(); > +#endif Nit: with IS_ENABLED() this does not need to be an #ifdef, but rather if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) reserve_crashkernel(); The same applies to the cases below. > + > high_memory = __va(memblock_end_of_DRAM() - 1) + 1; > } > > @@ -357,11 +385,13 @@ void __init bootmem_init(void) > */ > dma_contiguous_reserve(arm64_dma_phys_limit); > > +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) > /* > * request_standard_resources() depends on crashkernel's memory being > * reserved, so do it here. > */ > reserve_crashkernel(); > +#endif > > memblock_dump_all(); > } > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index acfae9b41cc8..884b2c6d6cd9 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -517,7 +517,7 @@ static void __init map_mem(pgd_t *pgdp) > */ > BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end)); > > - if (can_set_direct_map() || crash_mem_map || IS_ENABLED(CONFIG_KFENCE)) > + if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) > flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > > /* > @@ -528,6 +528,18 @@ static void __init map_mem(pgd_t *pgdp) > */ > memblock_mark_nomap(kernel_start, kernel_end - kernel_start); > > +#if IS_ENABLED(CONFIG_KEXEC_CORE) > + > +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) > + if (crash_mem_map) > + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > +#else > + if (crashk_res.end) > + memblock_mark_nomap(crashk_res.start, > + resource_size(&crashk_res)); > +#endif > + > +#endif > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > if (start >= end) > @@ -554,6 +566,21 @@ static void __init map_mem(pgd_t *pgdp) > __map_memblock(pgdp, kernel_start, kernel_end, > PAGE_KERNEL, NO_CONT_MAPPINGS); > memblock_clear_nomap(kernel_start, kernel_end - kernel_start); > +#if IS_ENABLED(CONFIG_KEXEC_CORE) && \ > + !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32) > + /* > + * Use page-level mappings here so that we can shrink the region > + * in page granularity and put back unused memory to buddy system > + * through /sys/kernel/kexec_crash_size interface. > + */ > + if (crashk_res.end) { > + __map_memblock(pgdp, crashk_res.start, crashk_res.end + 1, > + PAGE_KERNEL, > + NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS); > + memblock_clear_nomap(crashk_res.start, > + resource_size(&crashk_res)); > + } > +#endif > } > > void mark_rodata_ro(void) > -- > 2.35.1 > -- Sincerely yours, Mike.