Re: [Qemu-devel] [RFC PATCH 1/3] hw/arm/virt: add hotplug memory support

[Peter Maydell]

On 20 July 2016 at 01:49, Kwangwoo Lee <address@hidden> wrote:
> Add hotplug memory feature on aarch64 virt platfom. This patch is
> required to emulate a DIMM type memory like NVDIMM.
>
> Signed-off-by: Kwangwoo Lee <address@hidden>
> ---
>  default-configs/aarch64-softmmu.mak |   1 +
>  hw/arm/virt.c                       | 110 
> ++++++++++++++++++++++++++++++++++++
>  include/hw/arm/virt.h               |   3 +
>  3 files changed, 114 insertions(+)
>
> diff --git a/default-configs/aarch64-softmmu.mak 
> b/default-configs/aarch64-softmmu.mak
> index 2449483..5790cd2 100644
> --- a/default-configs/aarch64-softmmu.mak
> +++ b/default-configs/aarch64-softmmu.mak
> @@ -7,3 +7,4 @@ CONFIG_AUX=y
>  CONFIG_DDC=y
>  CONFIG_DPCD=y
>  CONFIG_XLNX_ZYNQMP=y
> +CONFIG_MEM_HOTPLUG=y
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index a193b5a..f7ff411 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -58,6 +58,8 @@
>  #include "hw/smbios/smbios.h"
>  #include "qapi/visitor.h"
>  #include "standard-headers/linux/input.h"
> +#include "hw/mem/pc-dimm.h"
> +#include "hw/acpi/acpi.h"
>
>  /* Number of external interrupt lines to configure the GIC with */
>  #define NUM_IRQS 256
> @@ -91,6 +93,7 @@ typedef struct {
>      bool secure;
>      bool highmem;
>      int32_t gic_version;
> +    MemoryHotplugState hotplug_memory;
>  } VirtMachineState;
>
>  #define TYPE_VIRT_MACHINE   MACHINE_TYPE_NAME("virt")
> @@ -1376,6 +1379,40 @@ static void machvirt_init(MachineState *machine)
>      guest_info_state->machine_done.notify = virt_guest_info_machine_done;
>      qemu_add_machine_init_done_notifier(&guest_info_state->machine_done);
>
> +    /* initialize hotplug memory address space */
> +    if (machine->ram_size < machine->maxram_size) {
> +        ram_addr_t hotplug_mem_size = machine->maxram_size - 
> machine->ram_size;
> +
> +        if (machine->ram_slots > ACPI_MAX_RAM_SLOTS) {
> +            error_report("unsupported amount of memory slots: %"PRIu64,

"number of"

> +                     machine->ram_slots);
> +            exit(EXIT_FAILURE);
> +        }
> +
> +        if (QEMU_ALIGN_UP(machine->maxram_size,
> +                     TARGET_PAGE_SIZE) != machine->maxram_size) {
> +            error_report("maximum memory size must by aligned to multiple of 
> "

"must be"

> +                     "%d bytes", TARGET_PAGE_SIZE);
> +            exit(EXIT_FAILURE);
> +        }
> +
> +        vms->hotplug_memory.base =
> +                     ROUND_UP(vbi->memmap[VIRT_MEM].base + machine->ram_size,
> +                                              ARCH_VIRT_HOTPLUG_MEM_ALIGN);
> +
> +        if ((vms->hotplug_memory.base + hotplug_mem_size) <
> +            hotplug_mem_size) {

This expression is confusing. Is it trying to test for overflow?
When can that happen?

> +            error_report("unsupported amount of maximum memory: " 
> RAM_ADDR_FMT,
> +                     machine->maxram_size);
> +            exit(EXIT_FAILURE);
> +        }
> +
> +        memory_region_init(&vms->hotplug_memory.mr, OBJECT(vms),
> +                           "hotplug-memory", hotplug_mem_size);
> +        memory_region_add_subregion(sysmem, vms->hotplug_memory.base,
> +                                    &vms->hotplug_memory.mr);
> +    }
> +
>      vbi->bootinfo.ram_size = machine->ram_size;
>      vbi->bootinfo.kernel_filename = machine->kernel_filename;
>      vbi->bootinfo.kernel_cmdline = machine->kernel_cmdline;
> @@ -1448,9 +1485,75 @@ static void virt_set_gic_version(Object *obj, const 
> char *value, Error **errp)
>      }
>  }
>
> +static void virt_dimm_plug(HotplugHandler *hotplug_dev,
> +                         DeviceState *dev, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
> +    PCDIMMDevice *dimm = PC_DIMM(dev);
> +    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> +    MemoryRegion *mr = ddc->get_memory_region(dimm);
> +    Error *local_err = NULL;
> +    uint64_t align = memory_region_get_alignment(mr);
> +
> +    pc_dimm_memory_plug(dev, &vms->hotplug_memory, mr, align, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +out:
> +    error_propagate(errp, local_err);
> +}
> +
> +static void virt_dimm_unplug(HotplugHandler *hotplug_dev,
> +                           DeviceState *dev, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
> +    PCDIMMDevice *dimm = PC_DIMM(dev);
> +    PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(dimm);
> +    MemoryRegion *mr = ddc->get_memory_region(dimm);
> +    Error *local_err = NULL;
> +
> +    pc_dimm_memory_unplug(dev, &vms->hotplug_memory, mr);
> +    object_unparent(OBJECT(dev));
> +
> +    error_propagate(errp, local_err);
> +}
> +
> +static void virt_machinedevice_plug_cb(HotplugHandler *hotplug_dev,
> +                                      DeviceState *dev, Error **errp)
> +{
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        virt_dimm_plug(hotplug_dev, dev, errp);
> +    } else {
> +        error_setg(errp, "acpi: device plug request for not supported device"

"unsupported"

> +                   " type: %s", object_get_typename(OBJECT(dev)));
> +    }
> +}
> +
> +static void virt_machinedevice_unplug_cb(HotplugHandler *hotplug_dev,
> +                                        DeviceState *dev, Error **errp)
> +{
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        virt_dimm_unplug(hotplug_dev, dev, errp);
> +    } else {
> +        error_setg(errp, "acpi: device unplug for not supported device"

"unsupported"

> +                   " type: %s", object_get_typename(OBJECT(dev)));
> +    }
> +}
> +
> +static HotplugHandler *virt_get_hotplug_handler(MachineState *machine,
> +                                             DeviceState *dev)
> +{
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +        return HOTPLUG_HANDLER(machine);
> +    }
> +    return NULL;
> +}
> +
>  static void virt_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> +    HotplugHandlerClass *hc = HOTPLUG_HANDLER_CLASS(oc);
>
>      mc->init = machvirt_init;
>      /* Start max_cpus at the maximum QEMU supports. We'll further restrict
> @@ -1462,6 +1565,9 @@ static void virt_machine_class_init(ObjectClass *oc, 
> void *data)
>      mc->block_default_type = IF_VIRTIO;
>      mc->no_cdrom = 1;
>      mc->pci_allow_0_address = true;
> +    mc->get_hotplug_handler = virt_get_hotplug_handler;
> +    hc->plug = virt_machinedevice_plug_cb;
> +    hc->unplug = virt_machinedevice_unplug_cb;
>  }
>
>  static const TypeInfo virt_machine_info = {
> @@ -1471,6 +1577,10 @@ static const TypeInfo virt_machine_info = {
>      .instance_size = sizeof(VirtMachineState),
>      .class_size    = sizeof(VirtMachineClass),
>      .class_init    = virt_machine_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +         { TYPE_HOTPLUG_HANDLER },
> +         { }
> +    },
>  };
>
>  static void machvirt_machine_init(void)
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 9650193..35aa3cc 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -45,6 +45,9 @@
>
>  #define PPI(irq) ((irq) + 16)
>
> +/* 1GB alignment for hotplug memory region */
> +#define ARCH_VIRT_HOTPLUG_MEM_ALIGN (1ULL << 30)

Where does the 1GB alignment come from? Why do we need 1GB
alignment for the base but only 1KB alignment for the size?

> +
>  enum {
>      VIRT_FLASH,
>      VIRT_MEM,
> --
> 2.5.0

thanks
-- PMM