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Date: Thu, 04 Dec 2014 11:04:49 +0100
From: Eric Auger <eric.auger@...aro.org>
To: Christoffer Dall <christoffer.dall@...aro.org>
CC: eric.auger@...com, marc.zyngier@....com,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
kvm@...r.kernel.org, alex.williamson@...hat.com, agraf@...e.de,
gleb@...nel.org, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
patches@...aro.org, a.motakis@...tualopensystems.com
Subject: Re: [PATCH] KVM: arm/arm64: vgic: add init entry to VGIC KVM device
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@...aro.org>
>> ---
>> 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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