[PATCH v6 14/24] KVM: arm64: vgic-v3: vgic_v3_lpi_sync_pending_status

[Christoffer Dall]

On Thu, May 04, 2017 at 01:44:34PM +0200, Eric Auger wrote:
> this new helper synchronizes the irq pending_latch
> with the LPI pending bit status found in rdist pending table.
> As the status is consumed, we reset the bit in pending table.
> 
> As we need the PENDBASER_ADDRESS() in vgic-v3, let's move its
> definition in the irqchip header. We restore the full length
> of the field, ie [51:16]. Same for PROPBASER_ADDRESS with full
> field length of [51:12].

why into irqchip and not just the vgic header file?

> 
> Signed-off-by: Eric Auger <eric.auger at redhat.com>
> 
> ---
> 
> v6: new
> ---
>  include/linux/irqchip/arm-gic-v3.h |  2 ++
>  virt/kvm/arm/vgic/vgic-its.c       |  6 ++----
>  virt/kvm/arm/vgic/vgic-v3.c        | 44 ++++++++++++++++++++++++++++++++++++++
>  virt/kvm/arm/vgic/vgic.h           |  1 +
>  4 files changed, 49 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
> index 9519c7b..e09e5d7 100644
> --- a/include/linux/irqchip/arm-gic-v3.h
> +++ b/include/linux/irqchip/arm-gic-v3.h
> @@ -159,6 +159,8 @@
>  #define GICR_PROPBASER_RaWaWb	GIC_BASER_CACHEABILITY(GICR_PROPBASER, INNER, RaWaWb)
>  
>  #define GICR_PROPBASER_IDBITS_MASK			(0x1f)
> +#define GICR_PROPBASER_ADDRESS(x)	((x) & GENMASK_ULL(51, 12))
> +#define GICR_PENDBASER_ADDRESS(x)	((x) & GENMASK_ULL(51, 16))
>  
>  #define GICR_PENDBASER_SHAREABILITY_SHIFT		(10)
>  #define GICR_PENDBASER_INNER_CACHEABILITY_SHIFT		(7)
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index e7bb86a..f43ea30c 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -198,8 +198,6 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id,
>   */
>  #define BASER_ADDRESS(x)	((x) & GENMASK_ULL(47, 16))
>  #define CBASER_ADDRESS(x)	((x) & GENMASK_ULL(47, 12))
> -#define PENDBASER_ADDRESS(x)	((x) & GENMASK_ULL(47, 16))
> -#define PROPBASER_ADDRESS(x)	((x) & GENMASK_ULL(47, 12))
>  
>  #define GIC_LPI_OFFSET 8192
>  
> @@ -234,7 +232,7 @@ static struct its_collection *find_collection(struct vgic_its *its, int coll_id)
>  static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
>  			     struct kvm_vcpu *filter_vcpu)
>  {
> -	u64 propbase = PROPBASER_ADDRESS(kvm->arch.vgic.propbaser);
> +	u64 propbase = GICR_PROPBASER_ADDRESS(kvm->arch.vgic.propbaser);
>  	u8 prop;
>  	int ret;
>  
> @@ -346,7 +344,7 @@ static u32 max_lpis_propbaser(u64 propbaser)
>   */
>  static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
>  {
> -	gpa_t pendbase = PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser);
> +	gpa_t pendbase = GICR_PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser);
>  	struct vgic_irq *irq;
>  	int last_byte_offset = -1;
>  	int ret = 0;
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index be0f4c3..0d753ae 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -252,6 +252,50 @@ void vgic_v3_enable(struct kvm_vcpu *vcpu)
>  	vgic_v3->vgic_hcr = ICH_HCR_EN;
>  }
>  
> +int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)
> +{
> +	struct kvm_vcpu *vcpu;
> +	int byte_offset, bit_nr;
> +	gpa_t pendbase, ptr;
> +	bool status;
> +	u8 val;
> +	int ret;
> +
> +retry:
> +	vcpu = irq->target_vcpu;
> +	if (!vcpu)
> +		return 0;
> +
> +	pendbase = GICR_PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser);
> +
> +	byte_offset = irq->intid / BITS_PER_BYTE;
> +	bit_nr = irq->intid % BITS_PER_BYTE;
> +	ptr = pendbase + byte_offset;
> +
> +	ret = kvm_read_guest(kvm, ptr, &val, 1);
> +	if (ret)
> +		return ret;
> +
> +	status = val & (1 << bit_nr);
> +
> +	spin_lock(&irq->irq_lock);
> +	if (irq->target_vcpu != vcpu) {
> +		spin_unlock(&irq->irq_lock);
> +		goto retry;

Can the guest be continuously changing the configuration of the LPI and
cause this function to be called, which will efficiently hog this CPU
from the system, or am I being overly cautious here?

> +	}
> +	irq->pending_latch = status;
> +	vgic_queue_irq_unlock(vcpu->kvm, irq);
> +
> +	if (status) {
> +		/* clear consumed data */
> +		val &= ~(1 << bit_nr);
> +		ret = kvm_write_guest(kvm, ptr, &val, 1);
> +		if (ret)
> +			return ret;

Do we have a problem that if this is done twice within the same byte (on
different LPIs) then the data could be strangely out of sync?

Do we care?


Thanks,
-Christoffer

> +	}
> +	return 0;
> +}
> +
>  /* check for overlapping regions and for regions crossing the end of memory */
>  static bool vgic_v3_check_base(struct kvm *kvm)
>  {
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index b87f1c6..309ab64 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -157,6 +157,7 @@ void vgic_v3_get_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcr);
>  void vgic_v3_enable(struct kvm_vcpu *vcpu);
>  int vgic_v3_probe(const struct gic_kvm_info *info);
>  int vgic_v3_map_resources(struct kvm *kvm);
> +int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq);
>  int vgic_register_redist_iodevs(struct kvm *kvm, gpa_t dist_base_address);
>  
>  int vgic_register_its_iodevs(struct kvm *kvm);
> -- 
> 2.5.5
>