linux-kernel - Re: [PATCH v3 04/10] KVM: arm64: vgic-its: Walk the LPI xarray in vgic_copy_lpi

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Date: Sun, 18 Feb 2024 16:46:53 +0800
From: Zenghui Yu <yuzenghui@...wei.com>
To: Oliver Upton <oliver.upton@...ux.dev>
CC: <kvmarm@...ts.linux.dev>, <kvm@...r.kernel.org>, Marc Zyngier
	<maz@...nel.org>, James Morse <james.morse@....com>, Suzuki K Poulose
	<suzuki.poulose@....com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 04/10] KVM: arm64: vgic-its: Walk the LPI xarray in
 vgic_copy_lpi_list()

On 2024/2/17 2:41, Oliver Upton wrote:
> Start iterating the LPI xarray in anticipation of removing the LPI
> linked-list.
> 
> Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
> ---
>  arch/arm64/kvm/vgic/vgic-its.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
> index fb2d3c356984..9ce2edfadd11 100644
> --- a/arch/arm64/kvm/vgic/vgic-its.c
> +++ b/arch/arm64/kvm/vgic/vgic-its.c
> @@ -335,6 +335,7 @@ static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
>  int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr)
>  {
>  	struct vgic_dist *dist = &kvm->arch.vgic;
> +	XA_STATE(xas, &dist->lpi_xa, GIC_LPI_OFFSET);
>  	struct vgic_irq *irq;
>  	unsigned long flags;
>  	u32 *intids;
> @@ -353,7 +354,9 @@ int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr)
>  		return -ENOMEM;
>  
>  	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
> -	list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
> +	rcu_read_lock();
> +
> +	xas_for_each(&xas, irq, INTERRUPT_ID_BITS_ITS) {

We should use '1 << INTERRUPT_ID_BITS_ITS - 1' to represent the maximum
LPI interrupt ID.

>  		if (i == irq_count)
>  			break;
>  		/* We don't need to "get" the IRQ, as we hold the list lock. */
> @@ -361,6 +364,8 @@ int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr)
>  			continue;
>  		intids[i++] = irq->intid;
>  	}
> +
> +	rcu_read_unlock();
>  	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
>  
>  	*intid_ptr = intids;

Thanks,
Zenghui