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

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 22 Feb 2019 15:01:25 +0100
Auger Eric <eric.auger@redhat.com> wrote:

> 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
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)

> 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)  
> >   
>