Re: [Qemu-devel] [PATCH v7 08/17] hw/arm/virt: Implement kvm_type function for 4.0 machine

[Auger Eric <eric.auger@redhat.com>]

Hi Igor,

On 2/22/19 1:45 PM, Igor Mammedov wrote:
> On Wed, 20 Feb 2019 23:39:54 +0100
> Eric Auger <eric.auger@redhat.com> wrote:
> 
>> This patch implements the machine class kvm_type() callback.
>> It returns the number of bits requested 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.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>>
>> v6 -> v7:
>> - Introduce RAMBASE and rename add LEGACY_ prefix in that patch
>> - use local variables with explicit names in virt_set_memmap:
>>   device_memory_base, device_memory_size
>> - add an extended_memmap field in the class
>>
>> v5 -> v6:
>> - add some comments
>> - high IO region cannot start before 256GiB
>> ---
>>  hw/arm/virt.c         | 50 ++++++++++++++++++++++++++++++++++++++++++-
>>  include/hw/arm/virt.h |  2 ++
>>  2 files changed, 51 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index 9db602457b..ad3a0ad73d 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -1437,7 +1437,14 @@ static void machvirt_init(MachineState *machine)
>>      bool firmware_loaded = bios_name || drive_get(IF_PFLASH, 0, 0);
>>      bool aarch64 = true;
>>  
>> -    virt_set_memmap(vms);
>> +    /*
>> +     * In accelerated mode, the memory map is computed in kvm_type(),
>> +     * if set, to create a VM with the right number of IPA bits.
>> +     */
>> +
>> +    if (!mc->kvm_type || !kvm_enabled()) {
>> +        virt_set_memmap(vms);
>> +    }
>>  
>>      /* We can probe only here because during property set
>>       * KVM is not available yet
>> @@ -1814,6 +1821,36 @@ static HotplugHandler *virt_machine_get_hotplug_handler(MachineState *machine,
>>      return NULL;
>>  }
>>  
>> +/*
>> + * for arm64 kvm_type [7-0] encodes the requested number of bits
>> + * in the IPA address space
>> + */
>> +static int virt_kvm_type(MachineState *ms, const char *type_str)
>> +{
>> +    VirtMachineState *vms = VIRT_MACHINE(ms);
>> +    int max_vm_pa_size = kvm_arm_get_max_vm_ipa_size(ms);
>> +    int requested_pa_size;
>> +
>> +    /* we freeze the memory map to compute the highest gpa */
>> +    virt_set_memmap(vms);
>> +
>> +    requested_pa_size = 64 - clz64(vms->highest_gpa);
>> +
>> +    if (requested_pa_size > max_vm_pa_size) {
>> +        error_report("-m and ,maxmem option values "
>> +                     "require an IPA range (%d bits) larger than "
>> +                     "the one supported by the host (%d bits)",
>> +                     requested_pa_size, max_vm_pa_size);
>> +       exit(1);
>> +    }
>> +    /*
>> +     * By default we return 0 which corresponds to an implicit legacy
>> +     * 40b IPA setting. Otherwise we return the actual requested PA
>> +     * logsize
>> +     */
>> +    return requested_pa_size > 40 ? requested_pa_size : 0;
>> +}
>> +
>>  static void virt_machine_class_init(ObjectClass *oc, void *data)
>>  {
>>      MachineClass *mc = MACHINE_CLASS(oc);
>> @@ -1838,6 +1875,7 @@ 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;
>> @@ -1909,6 +1947,12 @@ static void virt_instance_init(Object *obj)
>>                                      "Valid values are none and smmuv3",
>>                                      NULL);
>>  
>> +    if (vmc->no_extended_memmap) {
>> +        vms->extended_memmap = false;
>> +    } else {
>> +        vms->extended_memmap = true;
>> +    }
>> +
>>      vms->irqmap = a15irqmap;
>>  }
>>  
>> @@ -1939,8 +1983,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(4, 0)
>>  
>>  static void virt_machine_3_1_options(MachineClass *mc)
>>  {
>> +    VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(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 */
>> +    vmc->no_extended_memmap = true;
> That's probably was asked in v6,
> do we really need this knob?
Yes the point was raised by Peter and I replied by another question ;-) "
But don't we want to forbid any pre-4.0 machvirt to run with more than
255GiB RAM?
"
without this knob:
- pre-4.0 machines will gain the capability to support more than 255GB
initial RAM if the kernel supports dynamic IPA setting
- pre-4.0 machines will gain PCDIMM/NVDIMM support
- another concern, maxmem and slots were not checked previously. If for
some reason - without instantiating the actual slots -, the user
specified it this was previously ignored. Now this is not anymore as
both parameters allow to compute the requested IPA range. So this may
fail now.
So I thought this was clearer to disable all the above for pre-4.0
machines. However if both of you agree, I will remove it.

thanks

Eric
> 
>>  }
>>  DEFINE_VIRT_MACHINE(3, 1)
>>  
>> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
>> index acad0400d8..7798462cb0 100644
>> --- a/include/hw/arm/virt.h
>> +++ b/include/hw/arm/virt.h
>> @@ -106,6 +106,7 @@ typedef struct {
>>      bool claim_edge_triggered_timers;
>>      bool smbios_old_sys_ver;
>>      bool no_highmem_ecam;
>> +    bool no_extended_memmap;
>>  } VirtMachineClass;
>>  
>>  typedef struct {
>> @@ -135,6 +136,7 @@ typedef struct {
>>      hwaddr highest_gpa;
>>      hwaddr device_memory_base;
>>      hwaddr device_memory_size;
>> +    bool extended_memmap;
>>  } VirtMachineState;
>>  
>>  #define VIRT_ECAM_ID(high) (high ? VIRT_HIGH_PCIE_ECAM : VIRT_PCIE_ECAM)
>