Re: [PATCH v6 9/9] x86: Pass memory range via E820 for kdump

Dave Young
2014-04-17T05:34:35Z

On 04/17/14 at 01:29pm, Dave Young wrote:
> On 04/14/14 at 10:55pm, WANG Chao wrote:
> > command line size is restricted by kernel, sometimes memmap=exactmap has
> > too many memory ranges to pass to cmdline. And also memmap=exactmap and
> > kASLR doesn't work together.
> >
> > A better approach, to pass the memory ranges for crash kernel to boot
> > into, is filling the memory ranges into E820.
> >
> > boot_params only got 128 slots for E820 map to fit in, when the number of
> > memory map exceeds 128, use setup_data to pass the rest as extended E820
> > memory map.
> >
> > kexec boot could also benefit from setup_data in case E820 memory map
> > exceeds 128.
> >
> > Now this new approach becomes default instead of memmap=exactmap.
> > saved_max_pfn users can specify --pass-memmap-cmdline to use the
> > exactmap approach.
> >
> > Signed-off-by: WANG Chao <chaowang@redhat.com>
> > Tested-by: Linn Crosetto <linn@hp.com>
> > Reviewed-by: Linn Crosetto <linn@hp.com>
> > ---
> > kexec/arch/i386/crashdump-x86.c | 6 +-
> > kexec/arch/i386/x86-linux-setup.c | 149 +++++++++++++++++++++++++-------------
> > kexec/arch/i386/x86-linux-setup.h | 1 +
> > 3 files changed, 103 insertions(+), 53 deletions(-)
> >
> > diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
> > index 7b618a6..4a1491b 100644
> > --- a/kexec/arch/i386/crashdump-x86.c
> > +++ b/kexec/arch/i386/crashdump-x86.c
> > @@ -979,7 +979,8 @@ int load_crashdump_segments(struct kexec_info *info, char* mod_cmdline,
> > dbgprintf("Created elf header segment at 0x%lx\n", elfcorehdr);
> > if (delete_memmap(memmap_p, &nr_memmap, elfcorehdr, memsz) < 0)
> > return -1;
> > - cmdline_add_memmap(mod_cmdline, memmap_p);
> > + if (arch_options.pass_memmap_cmdline)
> > + cmdline_add_memmap(mod_cmdline, memmap_p);
> > if (!bzImage_support_efi_boot)
> > cmdline_add_efi(mod_cmdline);
> > cmdline_add_elfcorehdr(mod_cmdline, elfcorehdr);
> > @@ -995,7 +996,8 @@ int load_crashdump_segments(struct kexec_info *info, char* mod_cmdline,
> > type = mem_range[i].type;
> > size = end - start + 1;
> > add_memmap(memmap_p, &nr_memmap, start, size, type);
> > - cmdline_add_memmap_acpi(mod_cmdline, start, end);
> > + if (arch_options.pass_memmap_cmdline)
> > + cmdline_add_memmap_acpi(mod_cmdline, start, end);
>
> Seems memmap_p contains the acpi ranges as well, so cmdline_add_memmap_acpi is
> not necessary anymore, just improve cmdline_add_memmap to add both RAM and ACPI
> ranges is enough.

CRASH_MAX_MEMMAP_NR is used in cmdline_add_memmap, it does not include the acpi
ranges, it looks strange, but anyway there's checking about cmdline overflow, tos
I think maybe this CRASH_MAX_MEMMAP_NR can be dropped.

>
> Thanks
> Dave
>
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