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

[Marcel Apfelbaum]

On 05/18/2016 05:31 PM, Igor Mammedov wrote:
> On Wed, 18 May 2016 17:12:09 +0300
> Marcel Apfelbaum <address@hidden> wrote:
>
> > On 05/18/2016 05:11 PM, Michael S. Tsirkin wrote:
> > > On Wed, May 18, 2016 at 03:59:29PM +0200, Igor Mammedov wrote:
> > > > On Sun, 15 May 2016 22:23:32 +0300
> > > > Marcel Apfelbaum <address@hidden> 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 <address@hidden>
> > > > 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.
> >
> > I'll try it.
> but only after you check if just presence of QWord would crash XP,
> so in case it doesn't crash we would keep _CRS simple static
> structure.
>
> I very vaguely recall that XP ignored QWord in PCI0._CRS,
> but it was long time ago so it won't hurt to recheck.

Thanks for the pointer!
Marcel

> > Thanks,
> > Marcel
> >
> > > > > ---
> > > > >    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)