Re: [Qemu-devel] [PATCH RFC 0/6] q35: add acpi pci hotplug support

[Alexander Bezzubikov]

Tried it on Win7 Enterprise SP1 - SHPC works well,  _OSC patches aren't
necessary (since pci-bridge has its own controller, I suppose).
On Linux guests it works when adding device from CLI with -device, but OS
seems to fail detecting the device when I add it with device_add from
monitor.
Also there're some issues with unplugging on Linux (haven't tested
unplugging on WIndows yet). That's the news.

2017-07-03 21:29 GMT+03:00 Michael S. Tsirkin <address@hidden>:

> On Mon, Jul 03, 2017 at 09:26:33PM +0300, Marcel Apfelbaum wrote:
> > On 03/07/2017 19:34, Michael S. Tsirkin wrote:
> > > On Mon, Jul 03, 2017 at 02:27:11PM +0200, Igor Mammedov wrote:
> > > > On Fri, 30 Jun 2017 10:25:05 +0300
> > > > Marcel Apfelbaum <address@hidden> wrote:
> > > >
> > > > [...]
> > > > >
> > > > > So for the modern systems not supporting PCI ACPI hotplug
> > > > > we don't need pci-bridges anyway, but for the older ones
> > > > > the ACPI code of the pci-bridge will be loaded into the
> > > > > ACPI namespace only if a pci-bridge is actually hot-plugged.
> > > >
> > > > just note that the set of 'older' guest OSes is limited to
> > > > one that do not support SHPC (i.e. to EOLed WinXP & co)
> > > > as for linux and more modern Windows SHPC hotplug should
> > > > just work without our ACPI hack (which taxes low memory
> > > > to keep acpi tables for bridges).
> > > >
> > > > So I'm in favor of Michael's suggestion to leave ACPI PCI
> > > > only in PC machine for old WinXP guests and to keep Q35
> > > > clean, where linux or newer Windows guests could just
> > > > use standard SHPC.
> > > >
> > > > [...]
> > >
> > > I didn't realize windows actually supports SHPC for PCI.
> >
> > Me neither, if Igor is right I am all for shpc hotplug
> > since Q35 is not supposed to support older guests.
> >
> > I remember I succeeded to enable shpc hotplug some time
> > ago, but only for Linux guests.
> >
> > Igor, do you have some spec/doc on newer Windows OSes that confirm
> > PCI shpc hotplug support?
>
> Just try it, easier than poking at specs which aren't always up to date.
>
> > >
> > > Do they correctly set _OSC Arg3, bit offset 1?
> > >     SHPC Native Hot Plug control
> > >     The OS sets this bit to 1 to request control over PCI/PCI-X
> Standard Hot-Plug Controller
> > >     (SHPC) hot plug. If the OS successfully receives control of this
> feature, it must track and
> > >     update the status of hot plug slots and handle hot plug events as
> described in the SHPC
> > >     Specification.
> > > I was under impression they only set bit 0.
> > >
> >
> > Alexandr, if modern Windows OSes do support shpc, it makes our
> > job easier, can you please try to enable shpc hotplug?
> >
> > Thanks,
> > Marcel
>
> No need to enable or even have a bridge for that at all -
> set the bit in _OSC, see what does guest enable.
>



-- 
Alexander Bezzubikov