[PATCH v2 04/10] KVM: arm/arm64: vgic: Allow HW irq to be encoded in LR

[marc.zyngier@arm.com (Marc Zyngier)]

On 17/07/15 20:50, Christoffer Dall wrote:
> On Wed, Jul 08, 2015 at 06:56:36PM +0100, Marc Zyngier wrote:
>> Now that struct vgic_lr supports the LR_HW bit and carries a hwirq
>> field, we can encode that information into the list registers.
>>
>> This patch provides implementations for both GICv2 and GICv3.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>>  include/linux/irqchip/arm-gic-v3.h |  3 +++
>>  include/linux/irqchip/arm-gic.h    |  3 ++-
>>  virt/kvm/arm/vgic-v2.c             | 16 +++++++++++++++-
>>  virt/kvm/arm/vgic-v3.c             | 21 ++++++++++++++++++---
>>  4 files changed, 38 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
>> index ffbc034..cf637d6 100644
>> --- a/include/linux/irqchip/arm-gic-v3.h
>> +++ b/include/linux/irqchip/arm-gic-v3.h
>> @@ -268,9 +268,12 @@
>>  
>>  #define ICH_LR_EOI			(1UL << 41)
>>  #define ICH_LR_GROUP			(1UL << 60)
>> +#define ICH_LR_HW			(1UL << 61)
>>  #define ICH_LR_STATE			(3UL << 62)
>>  #define ICH_LR_PENDING_BIT		(1UL << 62)
>>  #define ICH_LR_ACTIVE_BIT		(1UL << 63)
>> +#define ICH_LR_PHYS_ID_SHIFT		32
>> +#define ICH_LR_PHYS_ID_MASK		(0x3ffUL << ICH_LR_PHYS_ID_SHIFT)
>>  
>>  #define ICH_MISR_EOI			(1 << 0)
>>  #define ICH_MISR_U			(1 << 1)
>> diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
>> index 9de976b..ca88dad 100644
>> --- a/include/linux/irqchip/arm-gic.h
>> +++ b/include/linux/irqchip/arm-gic.h
>> @@ -71,11 +71,12 @@
>>  
>>  #define GICH_LR_VIRTUALID		(0x3ff << 0)
>>  #define GICH_LR_PHYSID_CPUID_SHIFT	(10)
>> -#define GICH_LR_PHYSID_CPUID		(7 << GICH_LR_PHYSID_CPUID_SHIFT)
>> +#define GICH_LR_PHYSID_CPUID		(0x3ff << GICH_LR_PHYSID_CPUID_SHIFT)
>>  #define GICH_LR_STATE			(3 << 28)
>>  #define GICH_LR_PENDING_BIT		(1 << 28)
>>  #define GICH_LR_ACTIVE_BIT		(1 << 29)
>>  #define GICH_LR_EOI			(1 << 19)
>> +#define GICH_LR_HW			(1 << 31)
>>  
>>  #define GICH_VMCR_CTRL_SHIFT		0
>>  #define GICH_VMCR_CTRL_MASK		(0x21f << GICH_VMCR_CTRL_SHIFT)
>> diff --git a/virt/kvm/arm/vgic-v2.c b/virt/kvm/arm/vgic-v2.c
>> index f9b9c7c..8d7b04d 100644
>> --- a/virt/kvm/arm/vgic-v2.c
>> +++ b/virt/kvm/arm/vgic-v2.c
>> @@ -48,6 +48,10 @@ static struct vgic_lr vgic_v2_get_lr(const struct kvm_vcpu *vcpu, int lr)
>>  		lr_desc.state |= LR_STATE_ACTIVE;
>>  	if (val & GICH_LR_EOI)
>>  		lr_desc.state |= LR_EOI_INT;
>> +	if (val & GICH_LR_HW) {
>> +		lr_desc.state |= LR_HW;
>> +		lr_desc.hwirq = (val & GICH_LR_PHYSID_CPUID) >> GICH_LR_PHYSID_CPUID_SHIFT;
>> +	}
>>  
>>  	return lr_desc;
>>  }
>> @@ -55,7 +59,9 @@ static struct vgic_lr vgic_v2_get_lr(const struct kvm_vcpu *vcpu, int lr)
>>  static void vgic_v2_set_lr(struct kvm_vcpu *vcpu, int lr,
>>  			   struct vgic_lr lr_desc)
>>  {
>> -	u32 lr_val = (lr_desc.source << GICH_LR_PHYSID_CPUID_SHIFT) | lr_desc.irq;
>> +	u32 lr_val;
>> +
>> +	lr_val = lr_desc.irq;
>>  
>>  	if (lr_desc.state & LR_STATE_PENDING)
>>  		lr_val |= GICH_LR_PENDING_BIT;
>> @@ -64,6 +70,14 @@ static void vgic_v2_set_lr(struct kvm_vcpu *vcpu, int lr,
>>  	if (lr_desc.state & LR_EOI_INT)
>>  		lr_val |= GICH_LR_EOI;
>>  
>> +	if (lr_desc.state & LR_HW) {
>> +		lr_val |= GICH_LR_HW;
>> +		lr_val |= (u32)lr_desc.hwirq << GICH_LR_PHYSID_CPUID_SHIFT;
>> +	}
>> +
>> +	if (lr_desc.irq < VGIC_NR_SGIS)
>> +		lr_val |= (lr_desc.source << GICH_LR_PHYSID_CPUID_SHIFT);
>> +
>>  	vcpu->arch.vgic_cpu.vgic_v2.vgic_lr[lr] = lr_val;
>>  }
>>  
>> diff --git a/virt/kvm/arm/vgic-v3.c b/virt/kvm/arm/vgic-v3.c
>> index dff0602..afbf925 100644
>> --- a/virt/kvm/arm/vgic-v3.c
>> +++ b/virt/kvm/arm/vgic-v3.c
>> @@ -67,6 +67,10 @@ static struct vgic_lr vgic_v3_get_lr(const struct kvm_vcpu *vcpu, int lr)
>>  		lr_desc.state |= LR_STATE_ACTIVE;
>>  	if (val & ICH_LR_EOI)
>>  		lr_desc.state |= LR_EOI_INT;
>> +	if (val & ICH_LR_HW) {
>> +		lr_desc.state |= LR_HW;
>> +		lr_desc.hwirq = (val >> ICH_LR_PHYS_ID_SHIFT) & GENMASK(9, 0);
>> +	}
>>  
>>  	return lr_desc;
>>  }
>> @@ -84,10 +88,17 @@ static void vgic_v3_set_lr(struct kvm_vcpu *vcpu, int lr,
>>  	 * Eventually we want to make this configurable, so we may revisit
>>  	 * this in the future.
>>  	 */
>> -	if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)
>> +	switch (vcpu->kvm->arch.vgic.vgic_model) {
>> +	case KVM_DEV_TYPE_ARM_VGIC_V3:
>>  		lr_val |= ICH_LR_GROUP;
>> -	else
>> -		lr_val |= (u32)lr_desc.source << GICH_LR_PHYSID_CPUID_SHIFT;
>> +		break;
>> +	case  KVM_DEV_TYPE_ARM_VGIC_V2:
>> +		if (lr_desc.irq < VGIC_NR_SGIS)
>> +			lr_val |= (u32)lr_desc.source << GICH_LR_PHYSID_CPUID_SHIFT;
> 
> I forget how this works: Why are we mixing GICH_LR_ stuff with ICH_LR_
> in the same function?  Aren't we always accessing these registers via
> the system registers interface from the hypervisor control point of
> view, regardless of which GIC version the guest sees?

That's a bit odd indeed, but there's a small trick here:

- GICv2 has the CPUID as part of the PHYSID field.
- GICv3 "native" has no CPUID
- GICv3, when used with a GICv2 guest, puts CPUID as part of the the
bottom 32bit of the ICH_LRn_EL2 register, which happens to be the VIRTID.

And that VIRTID, when used with a GICv2 guest, actually contains most of
the GICH_LR fields. Crucially, CPUID is located at VIRTID[12:10], which
happens to be GICH_LRn[12:10], exactly where it is on a GICv2.

Confusing? You bet. Oh, and that subtle difference seems to have been
removed from the architecture spec. Time to file a bug report.

> I guess my question here is: Why should this not be
> ICH_LR_PHYSID_CORE_SHIFT?

No, because as explained above, the CPUID doesn't belong to PHYSID...

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...