Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v7u1 31/31] x86, 64bit, mm: hibernate use generic mapping_init | Date | Fri, 04 Jan 2013 23:07:37 +0100 |
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On Friday, January 04, 2013 01:59:33 PM Yinghai Lu wrote: > On Fri, Jan 4, 2013 at 3:43 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote: > > On Thursday, January 03, 2013 04:48:51 PM Yinghai Lu wrote: > >> Make it only map range in pfn_mapped array. > > > > Can you please explain why that should be sufficient? > > It is needed. > > http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commitdiff;h=66520ebc2df3fe52eb4792f8101fac573b766baf > > Subject: [PATCH] x86, mm: Only direct map addresses that are marked as > E820_RAM > > Currently direct mappings are created for [ 0 to max_low_pfn<<PAGE_SHIFT ) > and [ 4GB to max_pfn<<PAGE_SHIFT ), which may include regions that are not > 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. > > > > > Have you tested it? > > > > No > > will update to > > Subject: [PATCH] x86, 64bit, mm: hibernate use generic mapping_init > > We should not set mapping for all under max_pfn. > That causes same problem that is fixed by > x86, mm: Only direct map addresses that are marked as E820_RAM > > Make it only map range in pfn_mapped array.
OK
Thanks, Rafael
-- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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