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

[Marcel Apfelbaum]

On 05/16/2016 11:24 AM, 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>
> > ---
> >   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)


Hi Igor,
Thanks for reviewing this series.

> >   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);
> that line should break linking on other targets which don't have
> pc_machine_get_reserved_memory_end()
> probably for got to add stub.

I cross-compiled all the targets with no problem.  It seems no stub is required.


> > +        if (!range->begin) {
> > +            range->begin = ROUND_UP(0x100000000ULL + pcms->above_4g_mem_size,
> > +                                    1ULL << 30);
> > +        }
> > +        range->end = 1ULL << 40; /* 40 bits physical */
> x86 specific in generic code

I am aware I put x86 code in the generic pci code, but I limited it with
    if (object_dynamic_cast(machine, TYPE_PC_MACHINE)) {
So we have a generic rule for getting the w64 range and a specific one for PC 
machines.

The alternative would be a w64 range per host-bridge, not bus.
Adding a pci_bus_get_w64_range function to PCIHostBridgeClass,
defaulting in current implementation for the base class and
overriding it for piix/q35 looks OK to you?

I thought about it, but it seemed over-engineered as opposed
to the 'simple' if statement, however I can try it if you think is better.

> ARM also has 64-bit PCI MMIO /git grep VIRT_PCIE_MMIO_HIGH/

I had a look and ARM does not use this infrastructure, it has its own 
abstractions,
a memmap list. This is the other reason I selected this implementation,
because is not really used by other targets (but it can be used in the future)


Thanks,
Marcel

> perhaps range should be a property of PCI bus,
> where a board sets its own values for start/size
>
> > +    } 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)