Commit fb21cb08 authored by Fuad Tabba's avatar Fuad Tabba Committed by Marc Zyngier
Browse files

KVM: arm64: Use standard seq_file iterator for vgic-debug debugfs 



The current implementation uses `vgic_state_iter` in `struct
vgic_dist` to track the sequence position. This effectively makes the
iterator shared across all open file descriptors for the VM.

This approach has significant drawbacks:
- It enforces mutual exclusion, preventing concurrent reads of the
  debugfs file (returning -EBUSY).
- It relies on storing transient iterator state in the long-lived
  VM structure (`vgic_dist`).

Refactor the implementation to use the standard `seq_file` iterator.
Instead of storing state in `kvm_arch`, rely on the `pos` argument
passed to the `start` and `next` callbacks, which tracks the logical
index specific to the file descriptor.

This change enables concurrent access and eliminates the
`vgic_state_iter` field from `struct vgic_dist`.

Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260202085721.3954942-4-tabba@google.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 5ab24969

arch/arm64/kvm/vgic/vgic-debug.c

+12 −28
Original line number Diff line number Diff line
@@ -104,58 +104,42 @@ static void *vgic_debug_start(struct seq_file *s, loff_t *pos) 
	struct kvm *kvm = s->private;

	struct vgic_state_iter *iter;



	mutex_lock(&kvm->arch.config_lock);

	iter = kvm->arch.vgic.iter;

	if (iter) {

		iter = ERR_PTR(-EBUSY);

		goto out;

	}



	iter = kmalloc(sizeof(*iter), GFP_KERNEL);

	if (!iter) {

		iter = ERR_PTR(-ENOMEM);

		goto out;

	}

	if (!iter)

		return ERR_PTR(-ENOMEM);



	iter_init(kvm, iter, *pos);

	kvm->arch.vgic.iter = iter;



	if (end_of_vgic(iter))

	if (end_of_vgic(iter)) {

		kfree(iter);

		iter = NULL;

out:

	mutex_unlock(&kvm->arch.config_lock);

	}



	return iter;

}



static void *vgic_debug_next(struct seq_file *s, void *v, loff_t *pos)

{

	struct kvm *kvm = s->private;

	struct vgic_state_iter *iter = kvm->arch.vgic.iter;

	struct vgic_state_iter *iter = v;



	++*pos;

	iter_next(kvm, iter);

	if (end_of_vgic(iter))

	if (end_of_vgic(iter)) {

		kfree(iter);

		iter = NULL;

	}

	return iter;

}



static void vgic_debug_stop(struct seq_file *s, void *v)

{

	struct kvm *kvm = s->private;

	struct vgic_state_iter *iter;

	struct vgic_state_iter *iter = v;



	/*

	 * If the seq file wasn't properly opened, there's nothing to clearn

	 * up.

	 */

	if (IS_ERR(v))

	if (IS_ERR_OR_NULL(v))

		return;



	mutex_lock(&kvm->arch.config_lock);

	iter = kvm->arch.vgic.iter;

	kfree(iter);

	kvm->arch.vgic.iter = NULL;

	mutex_unlock(&kvm->arch.config_lock);

}



static void print_dist_state(struct seq_file *s, struct vgic_dist *dist,

include/kvm/arm_vgic.h

+0 −3
Original line number Diff line number Diff line
@@ -302,9 +302,6 @@ struct vgic_dist { 


	struct xarray		lpi_xa;



	/* used by vgic-debug */

	struct vgic_state_iter *iter;



	/*

	 * GICv4 ITS per-VM data, containing the IRQ domain, the VPE

	 * array, the property table pointer as well as allocation