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

On 09/01/2008, Olof Johansson [off-list ref] wrote:

On Wed, Jan 09, 2008 at 08:33:53PM -0600, Linas Vepstas wrote:

quoted

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