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SubjectANNONCE: kexec

- Current ports now include i386 ppc and x86_64
Between the three of them I think there are some good examples
of what is needed to implement kexec. i386 and ppc can turn
off their mmu while x86_64 cannot, yet they all implement
identity mapped memory for code running in the processors
native mode.

- The code has been reviewed in preparation to sending to Andrew Morton
and hopefully mainline kernel inclusion.

- All uses of init_mm have been removed from the generic code

- Three new architecture specific hooks have been added.
int machine_kexec_prepare(struct kimage *image);
This does whatever architecture specific setup such
as allocating page tables that is needed for a given image.

void machine_kexec_cleanup(struct kimage *image);
When the image is removed instead of executed this does the
necessary cleanup.

void machine_shutdown(void);
device_shutdown cannot do everything. There are some pieces
of hardware that can only be shutdown by architecture specific
code. That needed architecture specific shutdown code is
generally common between machine_restart and machine_kexec,
and it needs a function to live in. In addition the
coming kexec_on_panic code path needs to do nothing what is
absolutely necessary, making the architecture specific shutdown
code inappropriate.

machine_shutdown is designed to hold the architecture specific
shutdown code.

REBOOT_CMD_KEXEC now calls machine_shutdown just before
machine_kexec. Which means the coming kexec_on_panic
implemenation can skip the unnecessary code by simply
not calling machine_shutdown.

- The i386 port now no longer uses init_mm and the implemetation
actually got simpler, and is much more robust in the face
of changing kernel infrastructure. Even making it work
with the 4G/4G patch should be simple.

- The x86_64 port has been tested on both Opterons and Xeons and
it works fine. Support for the 32bit x86 system call has not
been done but I have have a design for it if anyone cares.

- The jointly released port of kexec-tools-1.96 adds support for
x86_64, fixes a small glitch so it works on even a lowly 386
(tested) and adds support for linux style arguments to the i386

And a quick summary of the broken-out patches:

For i386 all I needed to do was add a shutdown the PIC.
For x86_64 sysfs support had not even been added for the legacy
PIC, so I ported the appropriate code from x86.

The x86 Multiprocessor Specification says the local
apic needs to be in either pic_mode (i.e. disabled) or
it needs to be in virtual wire mode. This patch restores
the local apic to virtual wirte mode when appropriate.


The x86 Multiprocessor Specification says access to the
legacy pic can either be direct to the cpu or it can
be through a io_apic programed in virtual wire mode.
This patch examines the ioapic interrupt routing and if an i8259
is connected to an ioapic in external interrupt mode it places
the given ioapic in virtual wirte mode instead of disabling
it completely.

Someone overzealously copied the resource reservation code
from x86 and was filter out 64bit io and memory resources. Ouch!
x86_64 needs this if it is going to allocation 64bit resources
properly and I need the 64bit memory resources if I want to see
all of the memory through /proc/iomem.

This patch simplys holds the generic part of kexec.

The x86_64 port, I simply factor out machine_shutdown from
machine_restart before I complete the port.

The i386 port. While factoring out machine_shutdown I make
rebooting on the bootstrap cpu the default as required by the
Multiprocessor Specification and expected by linux. With
a number of motherboard specific fixups become unnecessary.

homebrew-dol-support.ppc.patch [EXPERIMENTAL]
This is the ppc port. It still uses init_mm. So I first
make use_mm no-static. The port is not as mature as the x86
port but it should still work in the majority of cases. I don't
think the homebrew Dolphin OS support is clean enough to be
in the stable kernel but it is included in case people need
it and as a starting point for something better.

vmlinux-lds.i386.patch [EXPERIMENTAL]
highbzImage.i386.patch [EXPERIMENTAL]
In the discussions on how to implement kexec_on_panic a key
question has been can we build a kernel that executes in memory
the kernel that called panic had reserved.

These two patches are my proof of concept that we can make an
x86 kernel that will execute when loaded at a different memory
address. The first patch fixes up so it vmlinux
exports the appropriate physical addresses in it's ELF program
header and adds an option what memory location you want to boot
from. This is needed for the kexec_on_panic case if we want
the panic kernel to load somewhere else.

The patch makes the bzImage of an i386 kernel built with a
load_address other than bootable. This means you don't have
to use kexec to boot one of these kernels.

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