On 2014/7/8 15:55, Marc Zyngier wrote:
> On Tue, Jul 08 2014 at 4:42:56 am BST, wanghaibin <wanghaibin.wang@xxxxxxxxxx> wrote:
>> On 2014/6/19 17:45, Andre Przywara wrote:
>>
>>> With the introduction of a second emulated GIC model we need to let
>>> userspace specify the GIC model to use for each VM. Pass the
>>> userspace provided value down into the vGIC code to differentiate
>>> later.
>>>
>>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
>>> ---
>>> arch/arm/kvm/arm.c | 2 +-
>>> include/kvm/arm_vgic.h | 4 ++--
>>> virt/kvm/arm/vgic.c | 4 ++--
>>> 3 files changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>>> index 9ffe962..fa37fa1 100644
>>> --- a/arch/arm/kvm/arm.c
>>> +++ b/arch/arm/kvm/arm.c
>>> @@ -804,7 +804,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>> switch (ioctl) {
>>> case KVM_CREATE_IRQCHIP: {
>>> if (vgic_present)
>>> - return kvm_vgic_create(kvm);
>>> + return kvm_vgic_create(kvm, KVM_DEV_TYPE_ARM_VGIC_V2);
>>
>> Weird! In my opinion, qemu can use either KVM_CREATE_IRQCHIP interface
>> or kvm_device_ops interface to create the VGIC module. Is there
>> should be consider the VGIC_V3? I think qemu create the VGIC device
>> should be add the the version of VGIC info.
>
> Weird? No. KVM_CREATE_IRQCHIP is now a deprecated interface on ARM, and
> will only create a GICv2, forever. This interface doesn't offer any of
> the flexibility we require for GICv3. How would you tell the kernel that
> you want a GICv3 when KVM_CREATE_IRQCHIP doesn't even take a parameter?
OK, I get it! the qemu will test to create device first,
if success(now kvm has the capability), there will skip the old KVM_CREATE_IRQCHIP interface, and will real create device
in kvm_arm_gic_realize(here, we already know which version of gic will be created in virt.c or vexpress.c).
It seems that the KVM_CREATE_IRQCHIP interface will be unuseful for now and later kvm version,
and for the old kvm version, the KVM_CREATE_IRQCHIP interface may be useful, but it's not support VGICv3.
Thanks!
>
> The way to create a GICv3 is to use KVM_CREATE_DEVICE, which is
> flexible and extensible. GICv2 has already been converted to this.
>
> Thanks,
>
> M.
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