Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754599Ab2H2VR5 (ORCPT ); Wed, 29 Aug 2012 17:17:57 -0400 Received: from mail-vc0-f174.google.com ([209.85.220.174]:34455 "EHLO mail-vc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754510Ab2H2VRw (ORCPT ); Wed, 29 Aug 2012 17:17:52 -0400 MIME-Version: 1.0 In-Reply-To: <1346267046-6724-5-git-send-email-jacob.shin@amd.com> References: <1346267046-6724-1-git-send-email-jacob.shin@amd.com> <1346267046-6724-5-git-send-email-jacob.shin@amd.com> Date: Wed, 29 Aug 2012 14:17:51 -0700 X-Google-Sender-Auth: 0sqkBqmnmu1f0OhBgjT2kJ-7EmY Message-ID: Subject: Re: [PATCH 4/6] x86: Only direct map addresses that are marked as E820_RAM From: Yinghai Lu To: Jacob Shin Cc: X86-ML , LKML , "H. Peter Anvin" , Tejun Heo , Dave Young , Chao Wang , Vivek Goyal , Andreas Herrmann , Borislav Petkov Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5602 Lines: 142 On Wed, Aug 29, 2012 at 12:04 PM, Jacob Shin wrote: > Currently direct mappings are created for [ 0 to max_low_pfn< and [ 4GB to max_pfn< backed by actual DRAM. This is fine for holes under 4GB which are covered > by fixed and variable range MTRRs to be UC. However, we run into trouble > on higher memory addresses which cannot be covered by MTRRs. > > Our system with 1TB of RAM has an e820 that looks like this: > > BIOS-e820: [mem 0x0000000000000000-0x00000000000983ff] usable > BIOS-e820: [mem 0x0000000000098400-0x000000000009ffff] reserved > BIOS-e820: [mem 0x00000000000d0000-0x00000000000fffff] reserved > BIOS-e820: [mem 0x0000000000100000-0x00000000c7ebffff] usable > BIOS-e820: [mem 0x00000000c7ec0000-0x00000000c7ed7fff] ACPI data > BIOS-e820: [mem 0x00000000c7ed8000-0x00000000c7ed9fff] ACPI NVS > BIOS-e820: [mem 0x00000000c7eda000-0x00000000c7ffffff] reserved > BIOS-e820: [mem 0x00000000fec00000-0x00000000fec0ffff] reserved > BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved > BIOS-e820: [mem 0x00000000fff00000-0x00000000ffffffff] reserved > BIOS-e820: [mem 0x0000000100000000-0x000000e037ffffff] usable > BIOS-e820: [mem 0x000000e038000000-0x000000fcffffffff] reserved > BIOS-e820: [mem 0x0000010000000000-0x0000011ffeffffff] usable > > and so direct mappings are created for huge memory hole between > 0x000000e038000000 to 0x0000010000000000. Even though the kernel never > generates memory accesses in that region, since the page tables mark > them incorrectly as being WB, our (AMD) processor ends up causing a MCE > while doing some memory bookkeeping/optimizations around that area. > > This patch iterates through e820 and only direct maps ranges that are > marked as E820_RAM, and keeps track of those pfn ranges. Depending on > the alignment of E820 ranges, this may possibly result in using smaller > size (i.e. 4K instead of 2M or 1G) page tables. > > Signed-off-by: Jacob Shin > --- > arch/x86/include/asm/page_types.h | 9 ++++ > arch/x86/kernel/setup.c | 100 +++++++++++++++++++++++++++++++------ > arch/x86/mm/init.c | 2 + > arch/x86/mm/init_64.c | 6 +-- > 4 files changed, 99 insertions(+), 18 deletions(-) > > diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h > index e21fdd1..409047a 100644 > --- a/arch/x86/include/asm/page_types.h > +++ b/arch/x86/include/asm/page_types.h > @@ -3,6 +3,7 @@ > > #include > #include > +#include > > /* PAGE_SHIFT determines the page size */ > #define PAGE_SHIFT 12 > @@ -40,12 +41,20 @@ > #endif /* CONFIG_X86_64 */ > > #ifndef __ASSEMBLY__ > +#include > > extern int devmem_is_allowed(unsigned long pagenr); > > extern unsigned long max_low_pfn_mapped; > extern unsigned long max_pfn_mapped; > > +extern struct range pfn_mapped[E820_X_MAX]; > +extern int nr_pfn_mapped; > + > +extern void add_pfn_range_mapped(unsigned long start_pfn, unsigned long end_pfn); > +extern bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn); > +extern bool pfn_is_mapped(unsigned long pfn); > + > static inline phys_addr_t get_max_mapped(void) > { > return (phys_addr_t)max_pfn_mapped << PAGE_SHIFT; > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index d6e8c03..a2e392e 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -115,13 +115,47 @@ > #include > > /* > - * end_pfn only includes RAM, while max_pfn_mapped includes all e820 entries. > - * The direct mapping extends to max_pfn_mapped, so that we can directly access > - * apertures, ACPI and other tables without having to play with fixmaps. > + * max_low_pfn_mapped: highest direct mapped pfn under 4GB > + * max_pfn_mapped: highest direct mapped pfn over 4GB > + * > + * The direct mapping only covers E820_RAM regions, so the ranges and gaps are > + * represented by pfn_mapped > */ > unsigned long max_low_pfn_mapped; > unsigned long max_pfn_mapped; > > +struct range pfn_mapped[E820_X_MAX]; > +int nr_pfn_mapped; change to static? > + > +void add_pfn_range_mapped(unsigned long start_pfn, unsigned long end_pfn) > +{ > + nr_pfn_mapped = add_range_with_merge(pfn_mapped, E820_X_MAX, > + nr_pfn_mapped, start_pfn, end_pfn); > + nr_pfn_mapped = clean_sort_range(pfn_mapped, E820_X_MAX); > + > + max_pfn_mapped = max(max_pfn_mapped, end_pfn); > + > + if (end_pfn <= (1UL << (32 - PAGE_SHIFT))) > + max_low_pfn_mapped = max(max_low_pfn_mapped, end_pfn); > +} > + > +bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn) > +{ > + int i; > + > + for (i = 0; i < nr_pfn_mapped; i++) > + if ((start_pfn >= pfn_mapped[i].start) && > + (end_pfn <= pfn_mapped[i].end)) > + return true; > + > + return false; > +} > + > +bool pfn_is_mapped(unsigned long pfn) > +{ > + return pfn_range_is_mapped(pfn, pfn + 1); > +} wonder if those functions have to be in arch/x86/kernel/setup.c. also do we need to update the tracking array when we have do memory hot-remove? Thanks Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/