irqchip/riscv-imsic: Adjust the number of available guest irq files

Currently, KVM assumes the minimum of implemented HGEIE bits and
"BIT(gc->guest_index_bits) - 1" as the number of guest files available
across all CPUs. This will not work when CPUs have different number
of guest files because KVM may incorrectly allocate a guest file on a
CPU with fewer guest files.

To address above, during initialization, calculate the number of
available guest interrupt files according to MMIO resources and
constrain the number of guest interrupt files that can be allocated
by KVM.

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Acked-by: Thomas Gleixner <tglx@kernel.org>
Link: https://lore.kernel.org/r/20260104133457.57742-1-luxu.kernel@bytedance.com
Signed-off-by: Anup Patel <anup@brainfault.org>

Author: luxukernel

arch/riscv/kvm/aia.c

@@ -630,7 +630,7 @@ int kvm_riscv_aia_init(void)
 	 */
 	if (gc)
 		kvm_riscv_aia_nr_hgei = min((ulong)kvm_riscv_aia_nr_hgei,
-					    BIT(gc->guest_index_bits) - 1);
+					    gc->nr_guest_files);
 	else
 		kvm_riscv_aia_nr_hgei = 0;
 

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

@@ -784,7 +784,7 @@ static int __init imsic_parse_fwnode(struct fwnode_handle *fwnode,
 
 int __init imsic_setup_state(struct fwnode_handle *fwnode, void *opaque)
 {
-	u32 i, j, index, nr_parent_irqs, nr_mmios, nr_handlers = 0;
+	u32 i, j, index, nr_parent_irqs, nr_mmios, nr_guest_files, nr_handlers = 0;
 	struct imsic_global_config *global;
 	struct imsic_local_config *local;
 	void __iomem **mmios_va = NULL;
@@ -878,6 +878,7 @@ int __init imsic_setup_state(struct fwnode_handle *fwnode, void *opaque)
 	}
 
 	/* Configure handlers for target CPUs */
+	global->nr_guest_files = BIT(global->guest_index_bits) - 1;
 	for (i = 0; i < nr_parent_irqs; i++) {
 		rc = imsic_get_parent_hartid(fwnode, i, &hartid);
 		if (rc) {
@@ -918,6 +919,15 @@ int __init imsic_setup_state(struct fwnode_handle *fwnode, void *opaque)
 		local->msi_pa = mmios[index].start + reloff;
 		local->msi_va = mmios_va[index] + reloff;
 
+		/*
+		 * KVM uses global->nr_guest_files to determine the available guest
+		 * interrupt files on each CPU. Take the minimum number of guest
+		 * interrupt files across all CPUs to avoid KVM incorrectly allocating
+		 * an unexisted or unmapped guest interrupt file on some CPUs.
+		 */
+		nr_guest_files = (resource_size(&mmios[index]) - reloff) / IMSIC_MMIO_PAGE_SZ - 1;
+		global->nr_guest_files = min(global->nr_guest_files, nr_guest_files);
+
 		nr_handlers++;
 	}
 

include/linux/irqchip/riscv-imsic.h

@@ -68,6 +68,9 @@ struct imsic_global_config {
 	/* Number of guest interrupt identities */
 	u32					nr_guest_ids;
 
+	/* Number of guest interrupt files per core */
+	u32					nr_guest_files;
+
 	/* Per-CPU IMSIC addresses */
 	struct imsic_local_config __percpu	*local;
 };