Re: [RFC] /proc/efi_memmap

Khalid Aziz
2005-09-13T22:52:55Z

On Tue, 2005-09-13 at 12:30 -0700, Luck, Tony wrote:
> On Tue, Sep 13, 2005 at 10:05:03AM -0600, Khalid Aziz wrote:
> > The userspace kexec tools looks at the memory map to verify a new kernel
> > being loaded in memory will be loaded in memory that is normally
> > available for it. Same goes for initial ramdisk as well. kexec
> > opens /proc/iomem on x86 for this. I had sent a patch in July (subject
> > "[PATCH] /proc/iomem update") that provides same info in /proc/iomem as
> > x86 does and that will take care of kexec needs. I have already tested
> > kexec tool for ia64 with that patch and it works fine.
>
> I should dust that off and take a look at it. /proc/iomem seems a curious
> name for a file that contains this information.
>
> So what is the current state of kexec for ia64? I think that there
> are two modes of operation:
>
> 1) Fast reboot (bypasses f/w ... which takes a significant amount of
> the reboot time).
>
> 2) A means to getting a running kernel to take a crash dump.
>
> In case 1, the system is still running ... so kexec can load the new
> kernel from disk, and arrange for an orderly transfer of control from
> the old kernel to the new.
>
> In case 2, we need to plan ahead, and have the new kernel pre-loaded
> into some reserved memory so when the panic hits (or the INIT button
> is pressed) we don't need to do any I/O or memory allocation. We just
> leap to the new kernel. For this case ia64 would appear to have an
> advantage over other architectures ... we don't need to locate the new
> kernel at any particular address, so we can leave the original kernel
> untouched while we boot just using the reserved block of memory.
>
> What's working? What's still being developed? Can we get this into
> shape for 2.6.15?
>
> -Tony

A working kexec patch requires the EFI memory map walk rewrite patch (so
we can pass a pristine EFI memory map to the kernel being kexec'd)
and /proc/iomem patch (for kexec-tool to work). I have been dragging my
feet on kexec patch partially since those two have not been accepted
yet :) If you add those two patches, it makes it lot easier for me to
give you a final kexec patch.

--
Khalid

==================================
Khalid Aziz Open Source and Linux Organization
(970)898-9214 Hewlett-Packard
khalid.aziz@hp.com Fort Collins, CO

"The Linux kernel is subject to relentless development"
- Alessandro Rubini