KVM: arm64: vgic-v3: Don't require IRQs be disabled for LPI xarray lock

Now that releases of LPIs have been unnested from the ap_list_lock there
are no xarray writers that exist in a context where IRQs are already
disabled. As such we can relax the locking to the non-IRQ disabling
spinlock to guard the LPI xarray.

Note that there are still readers of the LPI xarray where IRQs are
disabled however the readers rely on RCU protection instead of the lock.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250905100531.282980-6-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index 4c777136ea5ffcc37a68d3a01660f857ba30d4a6..4c3c0d82e476018fb7319ed02bfb858489583058 100644 (file)
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -53,7 +53,7 @@ void kvm_vgic_early_init(struct kvm *kvm)
 {
        struct vgic_dist *dist = &kvm->arch.vgic;
 
-       xa_init_flags(&dist->lpi_xa, XA_FLAGS_LOCK_IRQ);
+       xa_init(&dist->lpi_xa);
 }
 
 /* CREATION */

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index f162206adb482ac0d2eb5c709ed36c4d508d1855..ce3e3ed3f29f0496e1ff4042608b4183c11edffe 100644 (file)
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -78,7 +78,6 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 {
        struct vgic_dist *dist = &kvm->arch.vgic;
        struct vgic_irq *irq = vgic_get_irq(kvm, intid), *oldirq;
-       unsigned long flags;
        int ret;
 
        /* In this case there is no put, since we keep the reference. */
@@ -89,7 +88,7 @@ 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);
+       ret = xa_reserve(&dist->lpi_xa, intid, GFP_KERNEL_ACCOUNT);
        if (ret) {
                kfree(irq);
                return ERR_PTR(ret);
@@ -104,7 +103,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
        irq->target_vcpu = vcpu;
        irq->group = 1;
 
-       xa_lock_irqsave(&dist->lpi_xa, flags);
+       xa_lock(&dist->lpi_xa);
 
        /*
         * There could be a race with another vgic_add_lpi(), so we need to
@@ -126,7 +125,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
        }
 
 out_unlock:
-       xa_unlock_irqrestore(&dist->lpi_xa, flags);
+       xa_unlock(&dist->lpi_xa);
 
        if (ret)
                return ERR_PTR(ret);

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index 480391a0dcadb7ca9d858c2ac17a0dc92ca481af..a21b482844ce845ab91413a4d146e91b7f63c1d1 100644 (file)
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -28,7 +28,7 @@ struct vgic_global kvm_vgic_global_state __ro_after_init = {
  *     kvm->arch.config_lock (mutex)
  *       its->cmd_lock (mutex)
  *         its->its_lock (mutex)
- *           vgic_dist->lpi_xa.xa_lock         must be taken with IRQs disabled
+ *           vgic_dist->lpi_xa.xa_lock
  *             vgic_cpu->ap_list_lock          must be taken with IRQs disabled
  *               vgic_irq->irq_lock            must be taken with IRQs disabled
  *
@@ -141,30 +141,29 @@ static __must_check bool vgic_put_irq_norelease(struct kvm *kvm, struct vgic_irq
 void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 {
        struct vgic_dist *dist = &kvm->arch.vgic;
-       unsigned long flags;
 
        if (!__vgic_put_irq(kvm, irq))
                return;
 
-       xa_lock_irqsave(&dist->lpi_xa, flags);
+       xa_lock(&dist->lpi_xa);
        vgic_release_lpi_locked(dist, irq);
-       xa_unlock_irqrestore(&dist->lpi_xa, flags);
+       xa_unlock(&dist->lpi_xa);
 }
 
 static void vgic_release_deleted_lpis(struct kvm *kvm)
 {
        struct vgic_dist *dist = &kvm->arch.vgic;
-       unsigned long flags, intid;
+       unsigned long intid;
        struct vgic_irq *irq;
 
-       xa_lock_irqsave(&dist->lpi_xa, flags);
+       xa_lock(&dist->lpi_xa);
 
        xa_for_each(&dist->lpi_xa, intid, irq) {
                if (irq->pending_release)
                        vgic_release_lpi_locked(dist, irq);
        }
 
-       xa_unlock_irqrestore(&dist->lpi_xa, flags);
+       xa_unlock(&dist->lpi_xa);
 }
 
 void vgic_flush_pending_lpis(struct kvm_vcpu *vcpu)