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

[Auger Eric]

Hi Igor,

On 2/22/19 3:39 PM, Igor Mammedov wrote:
> On Fri, 22 Feb 2019 15:01:25 +0100
> Auger Eric <address@hidden> wrote:
> 
>> Hi Igor,
>>
>> On 2/22/19 1:45 PM, Igor Mammedov wrote:
>>> On Wed, 20 Feb 2019 23:39:54 +0100
>>> Eric Auger <address@hidden> 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 <address@hidden>
>>>>
>>>> ---
>>>>
>>>> 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
> should be fine, you shouldn't be able to start old QEMU with more than 255Gb
> 
>> - pre-4.0 machines will gain PCDIMM/NVDIMM support
> ditto
> 
>> - 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.
> well that's in category of a broken setup even if QEMU didn't complain about
> it before. User should fix it instead of QEMU supporting madness.
> (I think that such invariant doesn't even deserve deprecation process)

OK. So I will remove the knob in the next release.

thanks

Eric
> 
>> 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)  
>>>   
>>
>