Re: [BUG] powerpc does not save msi state [was Re: [PATCH 5/7] pci: Export the pci_restore_msi_state() function

On Fri, Oct 19, 2007 at 05:53:08PM -0700, David Miller wrote:

From: linas@austin.ibm.com (Linas Vepstas)
Date: Fri, 19 Oct 2007 19:46:10 -0500

quoted

FWIW, it looks like not all that many arches do this; the output
for grep -r address_hi * is pretty thin. Then, looking at
i386/kernel/io_apic.c as an example, one can see that the 
msi state save happens "by accident" if CONFIG_SMP is enabled;
and so its surely broekn on uniprocesor machines.

I don't see this, in all cases write_msi_msg() will transfer
the given "*msg" to entry->msg by this assignment in
drivers/pci/msi.c:

void write_msi_msg(unsigned int irq, struct msi_msg *msg)
{
 ...
	entry->msg = *msg;
}

So as long as write_msi_msg() is invoked, it will be saved
properly.

As Michael Ellerman points out, the pseries msi setup is done
by firmware, and so this bit never happens. 

As discussed in the other thread, I'll try to set up a patch
for an arch callback for restoring msi state.

-linas