[PATCH 3/3] KVM: arm64: vgic: Tear down what vgic_init() created when it fails

[Fuad Tabba <fuad.tabba@linux.dev>]

Once kvm_vgic_dist_init() has succeeded, every later failure in
vgic_init() returns with the SPI array still allocated. A failure after
vgic_v4_init() has also succeeded, which today means only
kvm_vgic_setup_default_irq_routing(), leaves the vPE array behind as
well.

A failed vgic_init() leaves kvm_arch_vcpu_precreate() admitting new
vCPUs, so a retry of KVM_DEV_ARM_VGIC_CTRL_INIT reaches
vgic_v4_init()'s early return with an array that no longer covers every
vCPU, and vgic_v3_load()'s WARN_ON(vgic_v4_load()) fires on the first
one it misses.

Release both on the two paths that can reach them, so the ioctl is all
or nothing and a retry starts from scratch. dist->nr_spis stays frozen,
since the SPI count cannot change once vgic_init() has supplied it.

Fixes: 74fe55dc9ab7 ("KVM: arm/arm64: GICv4: Add init/teardown of the per-VM vPE irq domain")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260807105558.73D701F000E9@smtp.kernel.org/
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 arch/arm64/kvm/vgic/vgic-init.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index 4012df6002ea6..7493fded53acc 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -462,7 +462,7 @@ int vgic_init(struct kvm *kvm)
 		if (vgic_supports_direct_irqs(kvm)) {
 			ret = vgic_v4_init(kvm);
 			if (ret)
-				return ret;
+				goto out_teardown;
 		}
 	} else {
 		ret = vgic_v5_init(kvm);
@@ -475,12 +475,19 @@ int vgic_init(struct kvm *kvm)
 
 	ret = kvm_vgic_setup_default_irq_routing(kvm);
 	if (ret)
-		return ret;
+		goto out_teardown;
 
 	vgic_debug_init(kvm);
 	dist->initialized = true;
 
 	return 0;
+
+out_teardown:
+	vgic_v4_teardown(kvm);
+	kfree(dist->spis);
+	dist->spis = NULL;
+
+	return ret;
 }
 
 static void kvm_vgic_dist_destroy(struct kvm *kvm)
-- 
2.39.5