Re: [Qemu-devel] [PATCH v6 09/18] hw/arm/virt: Implement kvm_type function for 4.0 machine

[Peter Maydell]

On Tue, 5 Feb 2019 at 17:33, Eric Auger <address@hidden> wrote:
>
> This patch implements the machine class kvm_type() callback.
> It returns the max IPA shift needed to implement the whole GPA
> range including the RAM and IO regions located beyond.
> The returned value in passed though the KVM_CREATE_VM ioctl and
> this allows KVM to set the stage2 tables dynamically.
>
> At this stage the RAM limit still is limited to 255GB.
>
> Setting all the existing highmem IO regions beyond the RAM
> allows to have a single contiguous RAM region (initial RAM and
> possible hotpluggable device memory). That way we do not need
> to do invasive changes in the EDK2 FW to support a dynamic
> RAM base.
>
> Signed-off-by: Eric Auger <address@hidden>
>
> ---
>
> v5 -> v6:
> - add some comments
> - high IO region cannot start before 256GiB
> ---
>  hw/arm/virt.c         | 52 +++++++++++++++++++++++++++++++++++++++++--
>  include/hw/arm/virt.h |  2 ++
>  2 files changed, 52 insertions(+), 2 deletions(-)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 2b15839d0b..b90ffc2e5d 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1366,6 +1366,7 @@ static uint64_t virt_cpu_mp_affinity(VirtMachineState 
> *vms, int idx)
>
>  static void virt_set_memmap(VirtMachineState *vms)
>  {
> +    MachineState *ms = MACHINE(vms);
>      hwaddr base;
>      int i;
>
> @@ -1375,7 +1376,17 @@ static void virt_set_memmap(VirtMachineState *vms)
>          vms->memmap[i] = a15memmap[i];
>      }
>
> -    vms->high_io_base = 256 * GiB; /* Top of the legacy initial RAM region */
> +    /*
> +     * We now compute the base of the high IO region depending on the
> +     * amount of initial and device memory. The device memory start/size
> +     * is aligned on 1GiB. We never put the high IO region below 256GiB
> +     * so that if maxram_size is < 255GiB we keep the legacy memory map
> +     */
> +    vms->high_io_base = ROUND_UP(GiB + ms->ram_size, GiB) +
> +                        ROUND_UP(ms->maxram_size - ms->ram_size, GiB);

I don't understand this expression...

> +    if (vms->high_io_base < 256 * GiB) {
> +        vms->high_io_base = 256 * GiB;
> +    }
>      base = vms->high_io_base;
>
>      for (i = VIRT_LOWMEMMAP_LAST; i < ARRAY_SIZE(extended_memmap); i++) {
> @@ -1386,6 +1397,7 @@ static void virt_set_memmap(VirtMachineState *vms)
>          vms->memmap[i].size = size;
>          base += size;
>      }
> +    vms->highest_gpa = base - 1;
>  }
>
>  static void machvirt_init(MachineState *machine)
> @@ -1402,7 +1414,9 @@ static void machvirt_init(MachineState *machine)
>      bool firmware_loaded = bios_name || drive_get(IF_PFLASH, 0, 0);
>      bool aarch64 = true;
>
> -    virt_set_memmap(vms);
> +    if (!vms->extended_memmap) {
> +        virt_set_memmap(vms);
> +    }
>
>      /* We can probe only here because during property set
>       * KVM is not available yet
> @@ -1784,6 +1798,36 @@ static HotplugHandler 
> *virt_machine_get_hotplug_handler(MachineState *machine,
>      return NULL;
>  }
>
> +/*
> + * for arm64 kvm_type [7-0] encodes the IPA size shift
> + */
> +static int virt_kvm_type(MachineState *ms, const char *type_str)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(ms);
> +    int max_vm_phys_shift = kvm_arm_get_max_vm_phys_shift(ms);
> +    int max_pa_shift;
> +
> +    vms->extended_memmap = true;
> +
> +    virt_set_memmap(vms);
> +
> +    max_pa_shift = 64 - clz64(vms->highest_gpa);
> +
> +    if (max_pa_shift > max_vm_phys_shift) {
> +        error_report("-m and ,maxmem option values "
> +                     "require an IPA range (%d bits) larger than "
> +                     "the one supported by the host (%d bits)",
> +                     max_pa_shift, max_vm_phys_shift);
> +       exit(1);
> +    }

Presumably we should have some equivalent check for TCG, so
that we don't let the user create a setup which wants more
bits of physical address than the TCG CPU allows ?

> +    /*
> +     * By default we return 0 which corresponds to an implicit legacy
> +     * 40b IPA setting. Otherwise we return the actual requested IPA
> +     * logsize
> +     */
> +    return max_pa_shift > 40 ? max_pa_shift : 0;
> +}
> +
>  static void virt_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> @@ -1808,6 +1852,7 @@ static void virt_machine_class_init(ObjectClass *oc, 
> void *data)
>      mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
>      mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
>      mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
> +    mc->kvm_type = virt_kvm_type;
>      assert(!mc->get_hotplug_handler);
>      mc->get_hotplug_handler = virt_machine_get_hotplug_handler;
>      hc->plug = virt_machine_device_plug_cb;
> @@ -1911,6 +1956,9 @@ static void virt_machine_3_1_options(MachineClass *mc)
>  {
>      virt_machine_4_0_options(mc);
>      compat_props_add(mc->compat_props, hw_compat_3_1, hw_compat_3_1_len);
> +
> +    /* extended memory map is enabled from 4.0 onwards */
> +    mc->kvm_type = NULL;

When is there a difference between setting this to NULL,
and setting it to virt_kvm_type but having the memory
size be <= 256GiB ?

If there isn't any difference, why can't we just let the
pre-4.0 versions behave like the new ones? No existing
VM setup will have > 256GB of memory, so as long as there's
no behaviour change for the <=256GB case we don't need to
take special effort to ensure that the >256GB case continues
to give an error message, do we ?

>  }
>  DEFINE_VIRT_MACHINE(3, 1)
>
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 3dc7a6c5d5..c88f67a492 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -132,6 +132,8 @@ typedef struct {
>      uint32_t iommu_phandle;
>      int psci_conduit;
>      hwaddr high_io_base;
> +    hwaddr highest_gpa;
> +    bool extended_memmap;
>  } VirtMachineState;
>
>  #define VIRT_ECAM_ID(high) (high ? VIRT_HIGH_PCIE_ECAM : VIRT_PCIE_ECAM)
> --
> 2.20.1

thanks
-- PMM