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

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

On Sun, May 15, 2016 at 10:23:32PM +0300, Marcel Apfelbaum 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>
> ---
>  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

I don't want pci to depend on PC.
Pls find another way to do this.


> @@ -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();
An empty line won't hurt here after the declaration.

> +    if (object_dynamic_cast(machine, TYPE_PC_MACHINE)) {
> +        PCMachineState *pcms = PC_MACHINE(machine);

An empty line won't hurt here after the declaration.

> +        range->begin = pc_machine_get_reserved_memory_end(pcms);
> +        if (!range->begin) {
> +            range->begin = ROUND_UP(0x100000000ULL + pcms->above_4g_mem_size,
> +                                    1ULL << 30);

Why 30? what is the logic here?

> +        }
> +        range->end = 1ULL << 40; /* 40 bits physical */

This comment does not help. Physical what? And why is 40 bit right?

> +    } else {
> +        range->begin = range->end = 0;
> +        pci_for_each_device_under_bus(bus, pci_dev_get_w64, range);

When does this trigger?
Pls add a comment.

> +    }
>  }
>  
>  static bool pcie_has_upstream_port(PCIDevice *dev)
> -- 
> 2.4.3