genirq: Increase the number of IRQ descriptors

virt inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7BQMW
CVE: NA

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The deafault value of NR_IRQS is not sufficient to support GICv4.1
features and ~56K LPIs. This parameter would be too small for certain
server platforms where it has many IO devices and is capable of
direct injection of vSGI and vLPI features.

Currently, maximum of 64 + 8192 (IRQ_BITMAP_BITS) IRQ descriptors
are allowed. The vCPU creation fails after reaching count ~400 with
kvm-arm.vgic_v4_enable=1.

This patch increases NR_IRQS to 1^19 to cover 56K LPIs and 262144
vSGIs (16vPEs x 16).

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Tips: This is a temporary fix[1], but it has been able to solve the
problem. The latest upstream version[2] depends on the 'maple tree',
which is inappropriately introduced to the current kernel.

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Another Tips: According to Chao Liu and Chang Liao's suggestion,
modifying IRQ_BITMAP_BITS can achieve the same effect with less
impact. Compared with solution[2], solution[1] has a disadvantage:
the memory foot print increases as the number of VMs increases.

Link: https://lore.kernel.org/linux-arm-kernel/20230104023738.1258925-1-sdonthineni@nvidia.com/ [1]
Link: https://lore.kernel.org/all/20230519134902.1495562-1-sdonthineni@nvidia.com/#t [2]
Signed-off-by: NShanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: NChao Liu <liuchao173@huawei.com>
Signed-off-by: NChang Liao <liaochang1@huawei.com>
Signed-off-by: NKunkun Jiang <jiangkunkun@huawei.com>

kernel/irq/internals.h

@@ -12,7 +12,7 @@
 #include <linux/sched/clock.h>
 
 #ifdef CONFIG_SPARSE_IRQ
-# define IRQ_BITMAP_BITS	(NR_IRQS + 8196)
+# define IRQ_BITMAP_BITS	(1 << 19)
 #else
 # define IRQ_BITMAP_BITS	NR_IRQS
 #endif