Re: [PATCH 05/15] KVM: arm64: vgic: Get rid of the LPI linked-list

[Marc Zyngier <maz@kernel.org>]

On Wed, 24 Jan 2024 20:48:59 +0000,
Oliver Upton <oliver.upton@linux.dev> wrote:
> 
> All readers of LPI configuration have been transitioned to use the LPI
> xarray. Get rid of the linked-list altogether.
> 
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
>  arch/arm64/kvm/vgic/vgic-init.c | 1 -
>  arch/arm64/kvm/vgic/vgic-its.c  | 7 ++-----
>  arch/arm64/kvm/vgic/vgic.c      | 1 -
>  include/kvm/arm_vgic.h          | 1 -
>  4 files changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
> index 411719053107..e25672d6e846 100644
> --- a/arch/arm64/kvm/vgic/vgic-init.c
> +++ b/arch/arm64/kvm/vgic/vgic-init.c
> @@ -53,7 +53,6 @@ void kvm_vgic_early_init(struct kvm *kvm)
>  {
>  	struct vgic_dist *dist = &kvm->arch.vgic;
>  
> -	INIT_LIST_HEAD(&dist->lpi_list_head);
>  	INIT_LIST_HEAD(&dist->lpi_translation_cache);
>  	raw_spin_lock_init(&dist->lpi_list_lock);
>  	xa_init_flags(&dist->lpi_xa, XA_FLAGS_LOCK_IRQ);
> diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
> index a2d95a279798..0486d3779d11 100644
> --- a/arch/arm64/kvm/vgic/vgic-its.c
> +++ b/arch/arm64/kvm/vgic/vgic-its.c
> @@ -74,10 +74,8 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
>  	 * There could be a race with another vgic_add_lpi(), so we need to
>  	 * check that we don't add a second list entry with the same LPI.
>  	 */
> -	list_for_each_entry(oldirq, &dist->lpi_list_head, lpi_list) {
> -		if (oldirq->intid != intid)
> -			continue;
> -
> +	oldirq = xa_load(&dist->lpi_xa, intid);
> +	if (oldirq) {
>  		/* Someone was faster with adding this LPI, lets use that. */
>  		kfree(irq);
>  		irq = oldirq;
> @@ -99,7 +97,6 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
>  		return ERR_PTR(ret);
>  	}
>  
> -	list_add_tail(&irq->lpi_list, &dist->lpi_list_head);
>  	dist->lpi_list_count++;
>  
>  out_unlock:
> diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
> index d90c42ff051d..e58ce68e325c 100644
> --- a/arch/arm64/kvm/vgic/vgic.c
> +++ b/arch/arm64/kvm/vgic/vgic.c
> @@ -121,7 +121,6 @@ void __vgic_put_lpi_locked(struct kvm *kvm, struct vgic_irq *irq)
>  	if (!kref_put(&irq->refcount, vgic_irq_release))
>  		return;
>  
> -	list_del(&irq->lpi_list);
>  	xa_erase(&dist->lpi_xa, irq->intid);
>  	dist->lpi_list_count--;
>  
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 795b35656b54..39037db3fa90 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -277,7 +277,6 @@ struct vgic_dist {
>  	/* Protects the lpi_list and the count value below. */
>  	raw_spinlock_t		lpi_list_lock;
>  	struct xarray		lpi_xa;
> -	struct list_head	lpi_list_head;
>  	int			lpi_list_count;
>  
>  	/* LPI translation cache */

You seem to be missing some of it (patch against the full series, so
context will be wrong):

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index 46ff21fea785..3de41ee5e6ee 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -58,7 +58,6 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 		return ERR_PTR(ret);
 	}
 
-	INIT_LIST_HEAD(&irq->lpi_list);
 	INIT_LIST_HEAD(&irq->ap_list);
 	raw_spin_lock_init(&irq->irq_lock);
 
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index f3fc2cc922ce..4439039ccd45 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -118,7 +118,6 @@ struct irq_ops {
 struct vgic_irq {
 	raw_spinlock_t irq_lock;	/* Protects the content of the struct */
 	struct rcu_head rcu;
-	struct list_head lpi_list;	/* Used to link all LPIs together */
 	struct list_head ap_list;
 
 	struct kvm_vcpu *vcpu;		/* SGIs and PPIs: The VCPU


	M.

-- 
Without deviation from the norm, progress is not possible.