[PATCH v3 01/10] KVM: arm64: vgic: Store LPIs in an xarray

Oliver Upton
2024-02-16T18:42:09Z

Using a linked-list for LPIs is less than ideal as it of course requires
iterative searches to find a particular entry. An xarray is a better
data structure for this use case, as it provides faster searches and can
still handle a potentially sparse range of INTID allocations.

Start by storing LPIs in an xarray, punting usage of the xarray to a
subsequent change.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
arch/arm64/kvm/vgic/vgic-init.c | 3 +++
arch/arm64/kvm/vgic/vgic-its.c | 16 ++++++++++++++++
arch/arm64/kvm/vgic/vgic.c | 1 +
include/kvm/arm_vgic.h | 2 ++
4 files changed, 22 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index e949e1d0fd9f..411719053107 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -56,6 +56,7 @@ void kvm_vgic_early_init(struct kvm *kvm)
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);
}

/* CREATION */
@@ -366,6 +367,8 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)

if (vgic_supports_direct_msis(kvm))
vgic_v4_teardown(kvm);
+
+ xa_destroy(&dist->lpi_xa);
}

static void __kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index e2764d0ffa9f..fb2d3c356984 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -52,6 +52,12 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
if (!irq)
return ERR_PTR(-ENOMEM);

+ ret = xa_reserve_irq(&dist->lpi_xa, intid, GFP_KERNEL_ACCOUNT);
+ if (ret) {
+ kfree(irq);
+ return ERR_PTR(ret);
+ }
+
INIT_LIST_HEAD(&irq->lpi_list);
INIT_LIST_HEAD(&irq->ap_list);
raw_spin_lock_init(&irq->irq_lock);
@@ -86,12 +92,22 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
goto out_unlock;
}

+ ret = xa_err(xa_store(&dist->lpi_xa, intid, irq, 0));
+ if (ret) {
+ xa_release(&dist->lpi_xa, intid);
+ kfree(irq);
+ goto out_unlock;
+ }
+
list_add_tail(&irq->lpi_list, &dist->lpi_list_head);
dist->lpi_list_count++;

out_unlock:
raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);

+ if (ret)
+ return ERR_PTR(ret);
+
/*
* We "cache" the configuration table entries in our struct vgic_irq's.
* However we only have those structs for mapped IRQs, so we read in
diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index db2a95762b1b..c126014f8395 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -131,6 +131,7 @@ void __vgic_put_lpi_locked(struct kvm *kvm, struct vgic_irq *irq)
return;

list_del(&irq->lpi_list);
+ xa_erase(&dist->lpi_xa, irq->intid);
dist->lpi_list_count--;

kfree(irq);
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 8cc38e836f54..795b35656b54 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -13,6 +13,7 @@
#include <linux/spinlock.h>
#include <linux/static_key.h>
#include <linux/types.h>
+#include <linux/xarray.h>
#include <kvm/iodev.h>
#include <linux/list.h>
#include <linux/jump_label.h>
@@ -275,6 +276,7 @@ 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;

--
2.44.0.rc0.258.g7320e95886-goog