[SeaBIOS] [Qemu-devel] [PATCH RFC] seabios: add OSHP method stub

Michael S. Tsirkin mst at redhat.com
Tue Feb 14 14:37:28 CET 2012

On Tue, Feb 14, 2012 at 12:49:08PM +0000, Paul Brook wrote:
> > > In a nutshell, I don't know what a SHPC is (nor OSHP), so I'm looking
> > > for an additional Ack.
> > 
> > No problem, I'll get an Ack :)
> > Meanwhile - here's a summary, as far as I understand it.
> > 
> > Originally PCI SIG only defined the electrical
> > and mechanical requirements from hotplug, no standard
> > software interface. So it needed ACPI to drive device-specific registers
> > to actually do hotplug.
> > At some point PCISIG defined standard interfaces
> > for PCI hotplug. There are two of them: standard
> > hot plug controller (SHPC) for PCI and PCIE hotplug
> > for Express.
> > 
> > Now an OS can have a standard driver and use it
> > to activate hotplug functionality. This is OS hotplug (OSHP).
> So presumably this will work on targets that don't have ACPI?
> Assuming a competent guest OS of course.  Have you tested this?
> Paul

This being the qemu side of things? I run Linux
and verified that it calls OSHP and afterwards,
runs the native driver and handles hotplug/unplug
without invoking ACPI at all.

It seems that at least the SHPC driver in linux
doesn't work if you don't have an acpi table
with the OSHP method - not many people run with acpi=off
nowdays, so it's probably just a bug.
I'll check how hard it is to fix this.


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