Re: [Qemu-devel] [PATCH V5] hw/pci-host: Fix x86 Host Bridges 64bit PCI hole

[Marcel Apfelbaum <marcel@redhat.com>]

On 11/11/2017 17:25, Marcel Apfelbaum 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 2G for I4400FX chipset
> in order to comply with older Win32 Guest OSes
> and 32G for Q35 chipset.
> 
> Even if the new defaults of pci-hole64-size will appear in
> "info qtree" also for older machines, the property was
> not implemented so no changes will be visible to guests.
> 
> Note this is a regression since prev QEMU versions had
> some range reserved for 64bit PCI hotplug.
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> ---
> 

Hi Michael,

Can you please merge the patch for QEMU 2.11
if you have no further comments?
I think is an important fix and it worth
having it in 2.11 .

Thanks,
Marcel

> V4 -> V5:
>   - Renamed a local variable (Laszlo)
>   - Added a comment to q35 props (Eduardo)
> 
> V3 -> V4:
>   - Addressed Laszlo's comments:
>      - Added defines for pci-hole64 default size props.
>      - Rounded the hole64_end to 1G
>      - Moved some info to commit message
>   - Addressed Michael's comments:
>      - Added more comments.
>   - I kept Gerd's "review-by" tag since no functional changes were made.
> 
> V2 -> V3:
>   - Addressed Gerd's and others comments and re-enabled the pci-hole64-size
>     property defaulting it to 2G for I440FX and 32g for Q35.
>   - Even if the new defaults of pci-hole64-size will appear in "info qtree"
>     also for older machines, the property was not implemented so
>     no changes will be visible to guests.
> 
> 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)
>      - Init compat props to "off" instead of "false"
> 
>   hw/i386/pc.c              | 22 ++++++++++++++++++++++
>   hw/pci-host/piix.c        | 32 ++++++++++++++++++++++++++++++--
>   hw/pci-host/q35.c         | 42 +++++++++++++++++++++++++++++++++++++++---
>   include/hw/i386/pc.h      | 10 +++++++++-
>   include/hw/pci-host/q35.h |  1 +
>   5 files changed, 101 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index e11a65b545..fafe5ba5cd 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;
>   }
>   
> +/*
> + * The 64bit pci hole starts after "above 4G RAM" and
> + * potentially the space reserved for memory hotplug.
> + */
> +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;
> +    }
> +
> +    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 a7e2256870..a684a7cca9 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;
>   
> @@ -112,6 +113,9 @@ struct PCII440FXState {
>   #define I440FX_PAM_SIZE 7
>   #define I440FX_SMRAM    0x72
>   
> +/* Keep it 2G to comply with older win32 guests */
> +#define I440FX_PCI_HOST_HOLE64_SIZE_DEFAULT (1ULL << 31)
> +
>   /* Older coreboot versions (4.0 and older) read a config register that doesn't
>    * exist in real hardware, to get the RAM size from QEMU.
>    */
> @@ -238,29 +242,52 @@ static void i440fx_pcihost_get_pci_hole_end(Object *obj, Visitor *v,
>       visit_type_uint32(v, name, &value, errp);
>   }
>   
> +/*
> + * The 64bit PCI hole start is set by the Guest firmware
> + * as the address of the first 64bit PCI MEM resource.
> + * If no PCI device has resources on the 64bit area,
> + * the 64bit PCI hole will start after "over 4G RAM" and the
> + * reserved space for memory hotplug if any.
> + */
>   static void i440fx_pcihost_get_pci_hole64_start(Object *obj, Visitor *v,
>                                                   const char *name,
>                                                   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);
>   }
>   
> +/*
> + * The 64bit PCI hole end is set by the Guest firmware
> + * as the address of the last 64bit PCI MEM resource.
> + * Then it is expanded to the PCI_HOST_PROP_PCI_HOLE64_SIZE
> + * that can be configured by the user.
> + */
>   static void i440fx_pcihost_get_pci_hole64_end(Object *obj, Visitor *v,
>                                                 const char *name, void *opaque,
>                                                 Error **errp)
>   {
>       PCIHostState *h = PCI_HOST_BRIDGE(obj);
> +    I440FXState *s = I440FX_PCI_HOST_BRIDGE(obj);
> +    uint64_t hole64_start = pc_pci_hole64_start();
>       Range w64;
> -    uint64_t value;
> +    uint64_t value, hole64_end;
>   
>       pci_bus_get_w64_range(h->bus, &w64);
>       value = range_is_empty(&w64) ? 0 : range_upb(&w64) + 1;
> +    hole64_end = ROUND_UP(hole64_start + s->pci_hole64_size, 1ULL << 30);
> +    if (s->pci_hole64_fix && value < hole64_end) {
> +        value = hole64_end;
> +    }
>       visit_type_uint64(v, name, &value, errp);
>   }
>   
> @@ -863,8 +890,9 @@ static const char *i440fx_pcihost_root_bus_path(PCIHostState *host_bridge,
>   
>   static Property i440fx_props[] = {
>       DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, I440FXState,
> -                     pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
> +                     pci_hole64_size, I440FX_PCI_HOST_HOLE64_SIZE_DEFAULT),
>       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 ddaa7d1b44..6cb9a8d121 100644
> --- a/hw/pci-host/q35.c
> +++ b/hw/pci-host/q35.c
> @@ -37,6 +37,8 @@
>    * Q35 host
>    */
>   
> +#define Q35_PCI_HOST_HOLE64_SIZE_DEFAULT (1ULL << 35)
> +
>   static void q35_host_realize(DeviceState *dev, Error **errp)
>   {
>       PCIHostState *pci = PCI_HOST_BRIDGE(dev);
> @@ -99,29 +101,52 @@ static void q35_host_get_pci_hole_end(Object *obj, Visitor *v,
>       visit_type_uint32(v, name, &value, errp);
>   }
>   
> +/*
> + * The 64bit PCI hole start is set by the Guest firmware
> + * as the address of the first 64bit PCI MEM resource.
> + * If no PCI device has resources on the 64bit area,
> + * the 64bit PCI hole will start after "over 4G RAM" and the
> + * reserved space for memory hotplug if any.
> + */
>   static void q35_host_get_pci_hole64_start(Object *obj, Visitor *v,
>                                             const char *name, void *opaque,
>                                             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);
>   }
>   
> +/*
> + * The 64bit PCI hole end is set by the Guest firmware
> + * as the address of the last 64bit PCI MEM resource.
> + * Then it is expanded to the PCI_HOST_PROP_PCI_HOLE64_SIZE
> + * that can be configured by the user.
> + */
>   static void q35_host_get_pci_hole64_end(Object *obj, Visitor *v,
>                                           const char *name, void *opaque,
>                                           Error **errp)
>   {
>       PCIHostState *h = PCI_HOST_BRIDGE(obj);
> +    Q35PCIHost *s = Q35_HOST_DEVICE(obj);
> +    uint64_t hole64_start = pc_pci_hole64_start();
>       Range w64;
> -    uint64_t value;
> +    uint64_t value, hole64_end;
>   
>       pci_bus_get_w64_range(h->bus, &w64);
>       value = range_is_empty(&w64) ? 0 : range_upb(&w64) + 1;
> +    hole64_end = ROUND_UP(hole64_start + s->mch.pci_hole64_size, 1ULL << 30);
> +    if (s->pci_hole64_fix && value < hole64_end) {
> +        value = hole64_end;
> +    }
>       visit_type_uint64(v, name, &value, errp);
>   }
>   
> @@ -133,16 +158,25 @@ static void q35_host_get_mmcfg_size(Object *obj, Visitor *v, const char *name,
>       visit_type_uint64(v, name, &e->size, errp);
>   }
>   
> +/*
> + * NOTE: setting defaults for the mch.* fields in this table
> + * doesn't work, because mch is a separate QOM object that is
> + * zeroed by the object_initialize(&s->mch, ...) call inside
> + * q35_host_initfn().  The default values for those
> + * properties need to be initialized manually by
> + * q35_host_initfn() after the object_initialize() call.
> + */
>   static Property q35_host_props[] = {
>       DEFINE_PROP_UINT64(PCIE_HOST_MCFG_BASE, Q35PCIHost, parent_obj.base_addr,
>                           MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT),
>       DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, Q35PCIHost,
> -                     mch.pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
> +                     mch.pci_hole64_size, Q35_PCI_HOST_HOLE64_SIZE_DEFAULT),
>       DEFINE_PROP_UINT32("short_root_bus", Q35PCIHost, mch.short_root_bus, 0),
>       DEFINE_PROP_SIZE(PCI_HOST_BELOW_4G_MEM_SIZE, Q35PCIHost,
>                        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(),
>   };
>   
> @@ -174,7 +208,9 @@ static void q35_host_initfn(Object *obj)
>       object_property_add_child(OBJECT(s), "mch", OBJECT(&s->mch), NULL);
>       qdev_prop_set_int32(DEVICE(&s->mch), "addr", PCI_DEVFN(0, 0));
>       qdev_prop_set_bit(DEVICE(&s->mch), "multifunction", false);
> -
> +    /* mch's object_initialize resets the default value, set it again */
> +    qdev_prop_set_uint64(DEVICE(s), PCI_HOST_PROP_PCI_HOLE64_SIZE,
> +                         Q35_PCI_HOST_HOLE64_SIZE_DEFAULT);
>       object_property_add(obj, PCI_HOST_PROP_PCI_HOLE_START, "uint32",
>                           q35_host_get_pci_hole_start,
>                           NULL, NULL, NULL, NULL);
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 087d184ef5..ef438bd765 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -238,7 +238,6 @@ void pc_guest_info_init(PCMachineState *pcms);
>   #define PCI_HOST_PROP_PCI_HOLE64_SIZE  "pci-hole64-size"
>   #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)
>   
>   
>   void pc_pci_as_mapping_init(Object *owner, MemoryRegion *system_memory,
> @@ -249,6 +248,7 @@ 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 +375,14 @@ 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;
>   
>