Re: [PATCH] KVM: arm/arm64: vgic: add init entry to VGIC KVM device

[Eric Auger]

Hi Christoffer
On 12/03/2014 11:45 AM, Christoffer Dall wrote:
> On Tue, Dec 02, 2014 at 06:27:31PM +0100, Eric Auger wrote:
>> Since the advent of dynamic initialization of VGIC, this latter is
>> initialized very late, on the first vcpu run. This initialization
>> could be initiated much earlier by the user, as soon as it has
>> provided the requested dimensioning parameters:
>> - number of IRQs and number of vCPUs,
>> - DIST and CPU interface base address.
>>
>> One motivation behind being able to initialize the VGIC sooner is
>> related to the setup of IRQ injection in VFIO use case. The VFIO
>> signaling, especially when used along with irqfd must be set *after*
>> vgic initialization to prevent any virtual IRQ injection before
>> VGIC initialization. If virtual IRQ injection occurs before the VGIC
>> init, the IRQ cannot be injected and subsequent injection is blocked
>> due to VFIO completion mechanism (unmask/mask or forward/unforward).
>>
>> This patch adds a new entry to the VGIC KVM device that allows
>> the user to manually request the VGIC init:
>> - a new KVM_DEV_ARM_VGIC_GRP_CTRL group is introduced.
>> - Its first attribute is KVM_DEV_ARM_VGIC_CTRL_INIT
>>
>> The rationale behind introducing a group is to be able to add other
>> controls later on, if needed.
>>
>> Obviously, as soon as the init is done, the dimensioning parameters
>> cannot be changed.
> 
> you would need to add a check in the vcpu_create path,
check added in v2
 which I don't
> believe we currently have.  That may conflict with Andre's series so we
> need to coordinate.
> 
> We're also seeing this potentially being useful for migration, so my
> feeling is that the GICv3 patches should be rebased on this patch and
> this patch should include a check in the vcpu create path.
> 
>>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>> ---
>>  Documentation/virtual/kvm/devices/arm-vgic.txt | 11 +++++++++++
>>  arch/arm/include/uapi/asm/kvm.h                |  2 ++
>>  arch/arm64/include/uapi/asm/kvm.h              |  2 ++
>>  virt/kvm/arm/vgic.c                            | 14 +++++++++++++-
>>  4 files changed, 28 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt
>> index df8b0c7..80db43f 100644
>> --- a/Documentation/virtual/kvm/devices/arm-vgic.txt
>> +++ b/Documentation/virtual/kvm/devices/arm-vgic.txt
>> @@ -81,3 +81,14 @@ Groups:
>>      -EINVAL: Value set is out of the expected range
>>      -EBUSY: Value has already be set, or GIC has already been initialized
>>              with default values.
>> +
>> +  KVM_DEV_ARM_VGIC_GRP_CTRL
>> +  Attributes:
>> +    KVM_DEV_ARM_VGIC_CTRL_INIT
>> +      request the initialization of the VGIC, no additional parameter in
>> +      kvm_device_attr.addr.
>> +  Errors:
>> +    -ENXIO: distributor or CPU interface base address were not set prior
>> +            to that call
> 
> this should be more generic to also apply to GICv3, I would suggest:
> 
> "VGIC not properly configured as required prior to calling this
> attribute."
corrected
> 
> alternatively, the attribute should be KVM_DEV_ARM_VGIC_V2_CTRL_INIT.
> 
>> +    -EINVAL: number of vcpus is not known
> 
> can we have a different error code for this case?  ENODEV for example?
corrected

Thanks
Eric
> 
>> +    -ENOMEM: memory shortage when allocating vgic internal data
> 
>> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
>> index 77547bb..2499867 100644
>> --- a/arch/arm/include/uapi/asm/kvm.h
>> +++ b/arch/arm/include/uapi/asm/kvm.h
>> @@ -175,6 +175,8 @@ struct kvm_arch_memory_slot {
>>  #define   KVM_DEV_ARM_VGIC_OFFSET_SHIFT	0
>>  #define   KVM_DEV_ARM_VGIC_OFFSET_MASK	(0xffffffffULL << KVM_DEV_ARM_VGIC_OFFSET_SHIFT)
>>  #define KVM_DEV_ARM_VGIC_GRP_NR_IRQS	3
>> +#define KVM_DEV_ARM_VGIC_GRP_CTRL       4
>> +#define   KVM_DEV_ARM_VGIC_CTRL_INIT    0
>>  
>>  /* KVM_IRQ_LINE irq field index values */
>>  #define KVM_ARM_IRQ_TYPE_SHIFT		24
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 1ed4417..b35c95a 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -161,6 +161,8 @@ struct kvm_arch_memory_slot {
>>  #define   KVM_DEV_ARM_VGIC_OFFSET_SHIFT	0
>>  #define   KVM_DEV_ARM_VGIC_OFFSET_MASK	(0xffffffffULL << KVM_DEV_ARM_VGIC_OFFSET_SHIFT)
>>  #define KVM_DEV_ARM_VGIC_GRP_NR_IRQS	3
>> +#define KVM_DEV_ARM_VGIC_GRP_CTRL	4
>> +#define   KVM_DEV_ARM_VGIC_CTRL_INIT	0
>>  
>>  /* KVM_IRQ_LINE irq field index values */
>>  #define KVM_ARM_IRQ_TYPE_SHIFT		24
>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>> index b76c38c..2fe5bdb 100644
>> --- a/virt/kvm/arm/vgic.c
>> +++ b/virt/kvm/arm/vgic.c
>> @@ -2474,7 +2474,14 @@ static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
>>  
>>  		return ret;
>>  	}
>> -
>> +	case KVM_DEV_ARM_VGIC_GRP_CTRL: {
>> +		switch (attr->attr) {
>> +		case KVM_DEV_ARM_VGIC_CTRL_INIT:
>> +			r = kvm_vgic_init(dev->kvm);
>> +			return r;
>> +		}
>> +		break;
>> +	}
>>  	}
>>  
>>  	return -ENXIO;
>> @@ -2553,6 +2560,11 @@ static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
>>  		return vgic_has_attr_regs(vgic_cpu_ranges, offset);
>>  	case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
>>  		return 0;
>> +	case KVM_DEV_ARM_VGIC_GRP_CTRL:
>> +		switch (attr->attr) {
>> +		case KVM_DEV_ARM_VGIC_CTRL_INIT:
>> +			return 0;
>> +		}
>>  	}
>>  	return -ENXIO;
>>  }
>> -- 
>> 1.9.1
>>

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