Re: [PATCH V2 0/5] x86: Create direct mappings for E820_RAM only

[Dave Young]

On 08/14/2012 05:46 AM, Jacob Shin wrote:

> Currently kernel direct mappings are created for all pfns between
> [ 0 to max_low_pfn ) and [ 4GB to max_pfn ). When we introduce memory
> holes, we end up mapping memory ranges that are not backed by physical
> DRAM. This is fine for lower memory addresses which can be marked as UC
> by fixed/variable range MTRRs, however we run in to trouble with high
> addresses.
> 
> The following patchset creates direct mappings only for E820_RAM regions
> between 0 ~ max_low_pfn and 4GB ~ max_pfn. And leaves non-E820_RAM and
> memory holes unmapped.


Hi,

Chaowang did some kdump test in a kvm guest with this patchset, 2nd
kenrel just reboot after some ACPI printk, see below dmesg of 2nd kernel:

After a crash:
[snip]
I'm in purgatory
[    0.000000] Initializing cgroup subsys cpuset
[    0.000000] Initializing cgroup subsys cpu
[    0.000000] Linux version 3.5.0-0.23.el7.bz846531.x86_64 (mockbuild@)
(gcc version 4.7.1 20120720 (Red Hat 4.7.1-5) (GCC) ) #1 SMP Mon Aug 13
22:17:46 EDT 2012
[    0.000000] Command line:
BOOT_IMAGE=/vmlinuz-3.5.0-0.23.el7.bz846531.x86_64
root=/dev/mapper/vg_none-lv_root ro rd.md=0 rd.lvm.lv=vg_none/lv_swap
rd.dm=0 rd.lvm.lv=vg_none/lv_root rd.luks=0 LANG=en_US.UTF-8
console=ttyS0,115200  SYSFONT=True KEYTABLE=us earlyprintk=serial
irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off
earlyprintk=serial memmap=exactmap memmap=567K@64K
memmap=261552K@589824K elfcorehdr=851376K
[    0.000000] e820: BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000100-0x000000000009dbff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009dc00-0x000000000009ffff]
reserved
[    0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff]
reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000003fffdfff] usable
[    0.000000] BIOS-e820: [mem 0x000000003fffe000-0x000000003fffffff]
reserved
[    0.000000] BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff]
reserved
[    0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff]
reserved
[    0.000000] bootconsole [earlyser0] enabled
[    0.000000] ERROR: earlyprintk= earlyser already used
[    0.000000] e820: last_pfn = 0x3fffe max_arch_pfn = 0x400000000
[    0.000000] NX (Execute Disable) protection: active
[    0.000000] e820: user-defined physical RAM map:
[    0.000000] user: [mem 0x0000000000010000-0x000000000009dbff] usable
[    0.000000] user: [mem 0x0000000024000000-0x0000000033f6bfff] usable
[    0.000000] DMI 2.4 present.
[    0.000000] No AGP bridge found
[    0.000000] e820: last_pfn = 0x33f6c max_arch_pfn = 0x400000000
[    0.000000] PAT not supported by CPU.
[    0.000000] found SMP MP-table at [mem 0x000fdae0-0x000fdaef] mapped
at [ffff8800000fdae0]
[    0.000000] init_memory_mapping: [mem 0x24000000-0x33f6bfff]
[    0.000000] init_memory_mapping: [mem 0x00000000-0x000fffff]
[    0.000000] RAMDISK: [mem 0x3378a000-0x33f58fff]
[    0.000000] ACPI: RSDP 00000000000fd980 00014 (v00 BOCHS )
[    0.000000] ACPI: RSDT 000000003fffe5b0 00038 (v01 BOCHS  BXPCRSDT
00000001 BXPC 00000001)
[    0.000000] ACPI: FACP 000000003fffff80 00074 (v01 BOCHS  BXPCFACP
00000001 BXPC 00000001)
[    0.000000] ACPI: DSDT 000000003fffe5f0 01121 (v01   BXPC   BXDSDT
00000001 INTL 20100528)
[    0.000000] ACPI: FACS 000000003fffff40 00040
[    0.000000] ACPI: SSDT 000000003ffffea0 0009E (v01 BOCHS  BXPCSSDT
00000001 BXPC 00000001)
[    0.000000] ACPI: APIC 000000003ffffdb0 00078 (v01 BOCHS  BXPCAPIC
00000001 BXPC 00000001)
[    0.000000] ACPI: HPET 000000003ffffd70 00038 (v01 BOCHS  BXPCHPET
00000001 BXPC 00000001)
[    0.000000] ACPI: SSDT 000000003ffff720 00644 (v01   BXPC BXSSDTPC
00000001 INTL 20100528)

====2nd kernel reboot here=====


> 
> This revision of the patchset attempts to resolve comments and concerns
> from the following threads:
> 
> https://lkml.org/lkml/2012/8/11/95
> 
> and
> 
> https://lkml.org/lkml/2011/12/16/486
> 
> Jacob Shin (5):
>   x86: Only direct map addresses that are marked as E820_RAM
>   x86: find_early_table_space based on memory ranges that are being
>     mapped
>   x86: Keep track of direct mapped pfn ranges
>   x86: Fixup code testing if a pfn is direct mapped
>   x86: Move enabling of PSE and PGE out of init_memory_mapping
> 
>  arch/x86/include/asm/page_types.h |    9 +++
>  arch/x86/kernel/amd_gart_64.c     |    4 +-
>  arch/x86/kernel/cpu/amd.c         |    6 +-
>  arch/x86/kernel/setup.c           |  118 ++++++++++++++++++++++++++++++++-----
>  arch/x86/mm/init.c                |   72 +++++++++++-----------
>  arch/x86/mm/init_64.c             |    3 +-
>  arch/x86/platform/efi/efi.c       |    8 +--
>  arch/x86/platform/efi/efi_64.c    |    2 +
>  8 files changed, 157 insertions(+), 65 deletions(-)
> 



-- 
Thanks
Dave
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