Re: [PATCH 1/8] pseries: phyp dump: Docmentation

["Linas Vepstas" <linasvepstas@gmail.com>]

On 09/01/2008, Olof Johansson <olof@lixom.net> wrote:
> On Wed, Jan 09, 2008 at 08:33:53PM -0600, Linas Vepstas wrote:
>
> > Heh. That's the elbow-grease of this thing.  The easy part is to get
> > the core function working. The hard part is to test these various configs,
> > and when they don't work, figure out what went wrong. That will take
> > perseverence and brains.
>
> This just sounds like a whole lot of extra work to get a feature that
> already exists.

Well, no. kexec is horribly ill-behaved with respect to PCI. The
kexec kernel starts running with PCI devices in some random
state; maybe they're DMA'ing or who knows what. kexec tries
real hard to whack a few needed pci devices into submission
but it has been hit-n-miss, and the source of 90% of the kexec
headaches and debugging effort. Its not pretty.

If all pci-host bridges could shut-down or settle the bus, and
raise the #RST line high, and then if all BIOS'es supported
this, you'd be right. But they can't ....

--linas