Re: [Qemu-devel] [PATCH V2] hw/pci-host: Fix x86 Host Bridges 64bit PCI hole

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 18 Oct 2017 14:16:12 +0300
Marcel Apfelbaum <marcel@redhat.com> wrote:

> Currently there is no MMIO range over 4G
> reserved for PCI hotplug. Since the 32bit PCI hole
> depends on the number of cold-plugged PCI devices
> and other factors, it is very possible is too small
> to hotplug PCI devices with large BARs.
> 
> Fix it by reserving all the address space after
> RAM (and the reserved space for RAM hotplug),
> but no more than 40bits. The later seems to be
> QEMU's magic number for the Guest physical CPU addressable
> bits and is safe with respect to migration.
> 
> Note this is a regression since prev QEMU versions had
> some range reserved for 64bit PCI hotplug.
> 
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> ---
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> V1 -> V2:
>  Addressed Igor's comments:
>     - aligned the hole64 start to 1Gb
>      (I think all the computations took care of it already,
>       but it can't hurt)
see
        *val = cpu_to_le64(ROUND_UP(res_mem_end, 0x1ULL << 30));                 
        fw_cfg_add_file(fw_cfg, "etc/reserved-memory-end", val, sizeof(*val));

>     - Init compat props to "off" instead of "false"
>
> Thanks,
> Marcel
> 
>  hw/i386/pc.c              | 22 ++++++++++++++++++++++
>  hw/pci-host/piix.c        | 10 ++++++++++
>  hw/pci-host/q35.c         |  9 +++++++++
>  include/hw/i386/pc.h      | 10 ++++++++++
>  include/hw/pci-host/q35.h |  1 +
>  5 files changed, 52 insertions(+)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 05985d4927..d11eeacead 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1448,6 +1448,28 @@ void pc_memory_init(PCMachineState *pcms,
>      pcms->ioapic_as = &address_space_memory;
>  }
>  
> +uint64_t pc_pci_hole64_start(void)
> +{
> +    PCMachineState *pcms = PC_MACHINE(qdev_get_machine());
> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
> +    uint64_t hole64_start = 0;
> +
> +    if (pcmc->has_reserved_memory && pcms->hotplug_memory.base) {
> +        hole64_start = pcms->hotplug_memory.base;
> +        if (!pcmc->broken_reserved_end) {
> +            hole64_start += memory_region_size(&pcms->hotplug_memory.mr);
> +        }
> +    } else {
> +        hole64_start = 0x100000000ULL + pcms->above_4g_mem_size;
> +    }
> +
> +    if (hole64_start > PCI_HOST_PCI_HOLE64_END) {
> +        hole64_start = PCI_HOST_PCI_HOLE64_END;
> +    }
> +
> +    return ROUND_UP(hole64_start, 1ULL << 30);
> +}
> +
>  qemu_irq pc_allocate_cpu_irq(void)
>  {
>      return qemu_allocate_irq(pic_irq_request, NULL, 0);
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index dec345fd24..317a232972 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -50,6 +50,7 @@ typedef struct I440FXState {
>      PCIHostState parent_obj;
>      Range pci_hole;
>      uint64_t pci_hole64_size;
> +    bool pci_hole64_fix;
>      uint32_t short_root_bus;
>  } I440FXState;
>  
> @@ -243,11 +244,15 @@ static void i440fx_pcihost_get_pci_hole64_start(Object *obj, Visitor *v,
>                                                  void *opaque, Error **errp)
>  {
>      PCIHostState *h = PCI_HOST_BRIDGE(obj);
> +    I440FXState *s = I440FX_PCI_HOST_BRIDGE(obj);
>      Range w64;
>      uint64_t value;
>  
>      pci_bus_get_w64_range(h->bus, &w64);
>      value = range_is_empty(&w64) ? 0 : range_lob(&w64);
> +    if (!value && s->pci_hole64_fix) {
> +        value = pc_pci_hole64_start();
> +    }
>      visit_type_uint64(v, name, &value, errp);
>  }
>  
> @@ -256,11 +261,15 @@ static void i440fx_pcihost_get_pci_hole64_end(Object *obj, Visitor *v,
>                                                Error **errp)
>  {
>      PCIHostState *h = PCI_HOST_BRIDGE(obj);
> +    I440FXState *s = I440FX_PCI_HOST_BRIDGE(obj);
>      Range w64;
>      uint64_t value;
>  
>      pci_bus_get_w64_range(h->bus, &w64);
>      value = range_is_empty(&w64) ? 0 : range_upb(&w64) + 1;
> +    if (s->pci_hole64_fix && value < PCI_HOST_PCI_HOLE64_END) {
> +        value = PCI_HOST_PCI_HOLE64_END;
> +    }
>      visit_type_uint64(v, name, &value, errp);
>  }
>  
> @@ -857,6 +866,7 @@ static Property i440fx_props[] = {
>      DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, I440FXState,
>                       pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
>      DEFINE_PROP_UINT32("short_root_bus", I440FXState, short_root_bus, 0),
> +    DEFINE_PROP_BOOL("x-pci-hole64-fix", I440FXState, pci_hole64_fix, true),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
> index 1ff648e80c..641213f177 100644
> --- a/hw/pci-host/q35.c
> +++ b/hw/pci-host/q35.c
> @@ -104,11 +104,15 @@ static void q35_host_get_pci_hole64_start(Object *obj, Visitor *v,
>                                            Error **errp)
>  {
>      PCIHostState *h = PCI_HOST_BRIDGE(obj);
> +    Q35PCIHost *s = Q35_HOST_DEVICE(obj);
>      Range w64;
>      uint64_t value;
>  
>      pci_bus_get_w64_range(h->bus, &w64);
>      value = range_is_empty(&w64) ? 0 : range_lob(&w64);
> +    if (!value && s->pci_hole64_fix) {
> +        value = pc_pci_hole64_start();
> +    }
>      visit_type_uint64(v, name, &value, errp);
>  }
>  
> @@ -117,11 +121,15 @@ static void q35_host_get_pci_hole64_end(Object *obj, Visitor *v,
>                                          Error **errp)
>  {
>      PCIHostState *h = PCI_HOST_BRIDGE(obj);
> +    Q35PCIHost *s = Q35_HOST_DEVICE(obj);
>      Range w64;
>      uint64_t value;
>  
>      pci_bus_get_w64_range(h->bus, &w64);
>      value = range_is_empty(&w64) ? 0 : range_upb(&w64) + 1;
> +    if (s->pci_hole64_fix && value < PCI_HOST_PCI_HOLE64_END) {
> +        value = PCI_HOST_PCI_HOLE64_END;
> +    }
>      visit_type_uint64(v, name, &value, errp);
>  }
>  
> @@ -143,6 +151,7 @@ static Property q35_host_props[] = {
>                       mch.below_4g_mem_size, 0),
>      DEFINE_PROP_SIZE(PCI_HOST_ABOVE_4G_MEM_SIZE, Q35PCIHost,
>                       mch.above_4g_mem_size, 0),
> +    DEFINE_PROP_BOOL("x-pci-hole64-fix", Q35PCIHost, pci_hole64_fix, true),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 087d184ef5..82ea8f67f4 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -239,6 +239,7 @@ void pc_guest_info_init(PCMachineState *pcms);
>  #define PCI_HOST_BELOW_4G_MEM_SIZE     "below-4g-mem-size"
>  #define PCI_HOST_ABOVE_4G_MEM_SIZE     "above-4g-mem-size"
>  #define DEFAULT_PCI_HOLE64_SIZE (~0x0ULL)
> +#define PCI_HOST_PCI_HOLE64_END (0x1ULL << 40)
>  
>  
>  void pc_pci_as_mapping_init(Object *owner, MemoryRegion *system_memory,
> @@ -249,6 +250,7 @@ void pc_memory_init(PCMachineState *pcms,
>                      MemoryRegion *system_memory,
>                      MemoryRegion *rom_memory,
>                      MemoryRegion **ram_memory);
> +uint64_t pc_pci_hole64_start(void);
>  qemu_irq pc_allocate_cpu_irq(void);
>  DeviceState *pc_vga_init(ISABus *isa_bus, PCIBus *pci_bus);
>  void pc_basic_device_init(ISABus *isa_bus, qemu_irq *gsi,
> @@ -375,6 +377,14 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
>          .driver   = TYPE_X86_CPU,\
>          .property = "x-hv-max-vps",\
>          .value    = "0x40",\
> +    },{\
> +        .driver   = "i440FX-pcihost",\
> +        .property = "x-pci-hole64-fix",\
> +        .value    = "off",\
> +    },{\
> +        .driver   = "q35-pcihost",\
> +        .property = "x-pci-hole64-fix",\
> +        .value    = "off",\
>      },
>  
>  #define PC_COMPAT_2_9 \
> diff --git a/include/hw/pci-host/q35.h b/include/hw/pci-host/q35.h
> index 58983c00b3..8f4ddde393 100644
> --- a/include/hw/pci-host/q35.h
> +++ b/include/hw/pci-host/q35.h
> @@ -68,6 +68,7 @@ typedef struct Q35PCIHost {
>      PCIExpressHost parent_obj;
>      /*< public >*/
>  
> +    bool pci_hole64_fix;
>      MCHPCIState mch;
>  } Q35PCIHost;
>