Messages in this thread |  | | From | Shanker Donthineni <> | Subject | [PATCH 0/5] Increase the number of IRQ descriptors for SPARSEIRQ | Date | Sun, 29 Jan 2023 18:57:20 -0600 |
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The ARM64 architecture uses SPARSEIRQ with a default value of NR_IRQS, which is set to 64. This means that only 64+8192 IRQ descriptors are allowed, which may not be sufficient for modern ARM64 servers that have a large number of IO devices and GIC hardware that supports direct vSGI and vLPI injection features.
This limitation has caused issues when attempting to launch multiple virtual machines with GICv4.1 features, resulting in the error message 'kvm_err("VPE IRQ allocation failure\n")'. The root cause of this issue is the ~8K IRQ descriptor limit.
To address this issue, an initial proposal was made to define NR_IRQS to 2^19 for ARM64. However, Marc Zyngier suggested implementing a generic solution instead of hard-coded values. Thomas Gleixner advised to use the maple tree data structure and provided most of the necessary functions.
For more information, refer to the discussion thread at https://lore.kernel.org/linux-arm-kernel/20230104023738.1258925-1-sdonthineni@nvidia.com/.
This patch series converts the static memory allocation to dynamic using the maple tree, and increases the maximum number of IRQ descriptors to INT_MAX from NR_IRQS+8192. This change has been tested on an ARM64 server with CONFIG_SPARSE_IRQ=y, where 256 virtual machines were launched, creating a total of 128K+ IRQ descriptors, and IRQ injection was verified.
Tested with v6.2-rc5 along with Maple-Tree RCU mode bug fixes, as per the information available at this link: https://lore.kernel.org/all/20230109205336.3665937-1-surenb@google.com/
[PATCH 1/41] maple_tree: Be more cautious about dead nodes [PATCH 2/41] maple_tree: Detect dead nodes in mas_start() [PATCH 3/41] maple_tree: Fix freeing of nodes in rcu mode [PATCH 4/41] maple_tree: remove extra smp_wmb() from mas_dead_leaves() [PATCH 5/41] maple_tree: Fix write memory barrier of nodes once dead for RCU mode [PATCH 6/41] maple_tree: Add smp_rmb() to dead node detection
Shanker Donthineni (5): genirq: Use hlist for managing resend handlers genirq: Allocate IRQ descriptors at boot time for !SPARSEIRQ genirq: Introduce two helper functions genirq: Use the common function irq_expand_nr_irqs() genirq: Use the maple tree for IRQ descriptors management
include/linux/irqdesc.h | 3 ++ kernel/irq/chip.c | 1 + kernel/irq/internals.h | 5 +- kernel/irq/irqdesc.c | 117 ++++++++++++++++++++++------------------ kernel/irq/resend.c | 36 +++++++------ 5 files changed, 94 insertions(+), 68 deletions(-)
-- 2.25.1
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