Re: [Qemu-devel] [PATCH V2 2/4] pci: reserve 64 bit MMIO range for PCI hotplug

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, May 18, 2016 at 03:59:29PM +0200, Igor Mammedov wrote:
> On Sun, 15 May 2016 22:23:32 +0300
> Marcel Apfelbaum <marcel@redhat.com> wrote:
> 
> > Using the firmware assigned MMIO ranges for 64-bit PCI window
> > leads to zero space for hot-plugging PCI devices over 4G.
> > 
> > PC machines can use the whole CPU addressable range after
> > the space reserved for memory-hotplug.
> > 
> > Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> that patch also has side effect of unconditionally adding
> QWordMemory() resource in PCI0._CRS
> on all machine types with QEMU generated ACPI tables.
> 
> Have you tested that it won't break boot of legacy OSes
> (XP, WS2003, old linux with 32bit kernel)?

It's almost sure it break it.
Maybe you can check _REV in _CRS to work around this for XP.

> > ---
> >  hw/pci/pci.c | 16 ++++++++++++++--
> >  1 file changed, 14 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index bb605ef..44dd949 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -41,6 +41,7 @@
> >  #include "hw/hotplug.h"
> >  #include "hw/boards.h"
> >  #include "qemu/cutils.h"
> > +#include "hw/i386/pc.h"
> >  
> >  //#define DEBUG_PCI
> >  #ifdef DEBUG_PCI
> > @@ -2467,8 +2468,19 @@ static void pci_dev_get_w64(PCIBus *b, PCIDevice *dev, void *opaque)
> >  
> >  void pci_bus_get_w64_range(PCIBus *bus, Range *range)
> >  {
> > -    range->begin = range->end = 0;
> > -    pci_for_each_device_under_bus(bus, pci_dev_get_w64, range);
> > +    Object *machine = qdev_get_machine();
> > +    if (object_dynamic_cast(machine, TYPE_PC_MACHINE)) {
> > +        PCMachineState *pcms = PC_MACHINE(machine);
> > +        range->begin = pc_machine_get_reserved_memory_end(pcms);
> > +        if (!range->begin) {
> > +            range->begin = ROUND_UP(0x100000000ULL + pcms->above_4g_mem_size,
> > +                                    1ULL << 30);
> > +        }
> > +        range->end = 1ULL << 40; /* 40 bits physical */
> > +    } else {
> > +        range->begin = range->end = 0;
> > +        pci_for_each_device_under_bus(bus, pci_dev_get_w64, range);
> > +    }
> >  }
> >  
> >  static bool pcie_has_upstream_port(PCIDevice *dev)