Revert "irqchip/riscv-imsic: Embed the vector array in lpriv"

The __alloc_percpu() fails when the number of IDs are greater than 959
because size parameter of __alloc_percpu() must be less than 32768 (aka
PCPU_MIN_UNIT_SIZE). This failure is observed with KVMTOOL when AIA is
trap-n-emulated by in-kernel KVM because in this case KVM guest has 2047
interrupt IDs.

To address this issue, don't embed vector array in struct imsic_local_priv
until __alloc_percpu() support size parameter greater than 32768.

This reverts commit 79eaabc ("irqchip/riscv-imsic: Embed the vector
array in lpriv").

Signed-off-by: Anup Patel <anup.patel@oss.qualcomm.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20251223143544.1504217-1-anup.patel@oss.qualcomm.com

Author: avpatel

drivers/irqchip/irq-riscv-imsic-state.c

@@ -477,6 +477,7 @@ static void __init imsic_local_cleanup(void)
 		lpriv = per_cpu_ptr(imsic->lpriv, cpu);
 
 		bitmap_free(lpriv->dirty_bitmap);
+		kfree(lpriv->vectors);
 	}
 
 	free_percpu(imsic->lpriv);
@@ -490,8 +491,7 @@ static int __init imsic_local_init(void)
 	int cpu, i;
 
 	/* Allocate per-CPU private state */
-	imsic->lpriv = __alloc_percpu(struct_size(imsic->lpriv, vectors, global->nr_ids + 1),
-				      __alignof__(*imsic->lpriv));
+	imsic->lpriv = alloc_percpu(typeof(*imsic->lpriv));
 	if (!imsic->lpriv)
 		return -ENOMEM;
 
@@ -511,6 +511,12 @@ static int __init imsic_local_init(void)
 		timer_setup(&lpriv->timer, imsic_local_timer_callback, TIMER_PINNED);
 #endif
 
+		/* Allocate vector array */
+		lpriv->vectors = kcalloc(global->nr_ids + 1, sizeof(*lpriv->vectors),
+					 GFP_KERNEL);
+		if (!lpriv->vectors)
+			goto fail_local_cleanup;
+
 		/* Setup vector array */
 		for (i = 0; i <= global->nr_ids; i++) {
 			vec = &lpriv->vectors[i];

drivers/irqchip/irq-riscv-imsic-state.h

@@ -40,7 +40,7 @@ struct imsic_local_priv {
 #endif
 
 	/* Local vector table */
-	struct imsic_vector			vectors[];
+	struct imsic_vector			*vectors;
 };
 
 struct imsic_priv {