From: Cong Wang <[email protected]> This patch implements a comprehensive IPI-based communication system for multikernel environments, enabling data exchange between different kernel instances running on separate CPUs.
Key features include: - Generic IPI handler registration and callback mechanism allowing modules to register for multikernel communication events - Shared memory infrastructure using either boot parameter-specified or dynamically allocated physical memory regions - Per-CPU data buffers in shared memory for efficient IPI payload transfer up to 256 bytes per message - IRQ work integration for safe callback execution in interrupt context - PFN-based flexible shared memory APIs for page-level data sharing - Resource tracking integration for /proc/iomem visibility The implementation provides multikernel_send_ipi_data() for sending typed data to target CPUs and multikernel_register_handler() for receiving notifications. Shared memory is established during early boot and mapped using memremap() for cache-coherent access. This infrastructure enables heterogeneous computing scenarios where multikernel instances can coordinate and share data while maintaining isolation on their respective CPU cores. Note, as a proof-of-concept, we have only implemented the x86 part. Signed-off-by: Cong Wang <[email protected]> --- arch/x86/kernel/smp.c | 5 +- include/linux/multikernel.h | 81 ++++++++++ init/main.c | 2 + kernel/Makefile | 2 +- kernel/multikernel.c | 313 ++++++++++++++++++++++++++++++++++++ 5 files changed, 398 insertions(+), 5 deletions(-) create mode 100644 include/linux/multikernel.h create mode 100644 kernel/multikernel.c diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index 028cc423a772..3ee515e32383 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -272,10 +272,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_call_function_single) trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR); } -static void generic_multikernel_interrupt(void) -{ - pr_info("Multikernel interrupt\n"); -} +void generic_multikernel_interrupt(void); DEFINE_IDTENTRY_SYSVEC(sysvec_multikernel) { diff --git a/include/linux/multikernel.h b/include/linux/multikernel.h new file mode 100644 index 000000000000..12ed5e03f92e --- /dev/null +++ b/include/linux/multikernel.h @@ -0,0 +1,81 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 Multikernel Technologies, Inc. All rights reserved + */ +#ifndef _LINUX_MULTIKERNEL_H +#define _LINUX_MULTIKERNEL_H + +#include <linux/types.h> +#include <linux/irq_work.h> + +/** + * Multikernel IPI interface + * + * This header provides declarations for the multikernel IPI interface, + * allowing modules to register callbacks for IPI events and pass data + * between CPUs. + */ + +/* Maximum data size that can be transferred via IPI */ +#define MK_MAX_DATA_SIZE 256 + +/* Data structure for passing parameters via IPI */ +struct mk_ipi_data { + int sender_cpu; /* Which CPU sent this IPI */ + unsigned int type; /* User-defined type identifier */ + size_t data_size; /* Size of the data */ + char buffer[MK_MAX_DATA_SIZE]; /* Actual data buffer */ +}; + +/* Function pointer type for IPI callbacks */ +typedef void (*mk_ipi_callback_t)(struct mk_ipi_data *data, void *ctx); + +struct mk_ipi_handler { + mk_ipi_callback_t callback; + void *context; + struct mk_ipi_handler *next; + struct mk_ipi_data *saved_data; + struct irq_work work; +}; + +/** + * multikernel_register_handler - Register a callback for multikernel IPI + * @callback: Function to call when IPI is received + * @ctx: Context pointer passed to the callback + * + * Returns pointer to handler on success, NULL on failure + */ +struct mk_ipi_handler *multikernel_register_handler(mk_ipi_callback_t callback, void *ctx); + +/** + * multikernel_unregister_handler - Unregister a multikernel IPI callback + * @handler: Handler pointer returned from multikernel_register_handler + */ +void multikernel_unregister_handler(struct mk_ipi_handler *handler); + +/** + * multikernel_send_ipi_data - Send data to another CPU via IPI + * @cpu: Target CPU + * @data: Pointer to data to send + * @data_size: Size of data + * @type: User-defined type identifier + * + * This function copies the data to per-CPU storage and sends an IPI + * to the target CPU. + * + * Returns 0 on success, negative error code on failure + */ +int multikernel_send_ipi_data(int cpu, void *data, size_t data_size, unsigned long type); + +void generic_multikernel_interrupt(void); + +int __init multikernel_init(void); + +/* Flexible shared memory APIs (PFN-based) */ +int mk_send_pfn(int target_cpu, unsigned long pfn); +int mk_receive_pfn(struct mk_ipi_data *data, unsigned long *out_pfn); +void *mk_receive_map_page(struct mk_ipi_data *data); + +#define mk_receive_unmap_page(p) memunmap(p) + +#endif /* _LINUX_MULTIKERNEL_H */ diff --git a/init/main.c b/init/main.c index 5753e9539ae6..46a199bcb389 100644 --- a/init/main.c +++ b/init/main.c @@ -103,6 +103,7 @@ #include <linux/randomize_kstack.h> #include <linux/pidfs.h> #include <linux/ptdump.h> +#include <linux/multikernel.h> #include <net/net_namespace.h> #include <asm/io.h> @@ -955,6 +956,7 @@ void start_kernel(void) vfs_caches_init_early(); sort_main_extable(); trap_init(); + multikernel_init(); mm_core_init(); maple_tree_init(); poking_init(); diff --git a/kernel/Makefile b/kernel/Makefile index c60623448235..e5216610a4e7 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -10,7 +10,7 @@ obj-y = fork.o exec_domain.o panic.o \ extable.o params.o \ kthread.o sys_ni.o nsproxy.o \ notifier.o ksysfs.o cred.o reboot.o \ - async.o range.o smpboot.o ucount.o regset.o ksyms_common.o + async.o range.o smpboot.o ucount.o regset.o ksyms_common.o multikernel.o obj-$(CONFIG_MULTIUSER) += groups.o obj-$(CONFIG_VHOST_TASK) += vhost_task.o diff --git a/kernel/multikernel.c b/kernel/multikernel.c new file mode 100644 index 000000000000..74e2f84b7914 --- /dev/null +++ b/kernel/multikernel.c @@ -0,0 +1,313 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 Multikernel Technologies, Inc. All rights reserved + */ +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/smp.h> +#include <linux/percpu.h> +#include <linux/spinlock.h> +#include <linux/multikernel.h> +#include <linux/io.h> +#include <linux/ioport.h> +#include <asm/apic.h> +#include <linux/memblock.h> + +/* Memory parameters for shared region */ +#define MK_IPI_DATA_SIZE (sizeof(struct mk_ipi_data) * NR_CPUS) +#define MK_MEM_BASE_SIZE (sizeof(struct mk_shared_data)) +#define MK_MEM_SIZE (MK_MEM_BASE_SIZE + PAGE_SIZE) + +/* Boot parameter for physical address */ +static unsigned long mk_phys_addr_param; + +/* Parse multikernel physical address from kernel command line */ +static int __init multikernel_phys_addr_setup(char *str) +{ + return kstrtoul(str, 0, &mk_phys_addr_param); +} +early_param("mk_shared_memory", multikernel_phys_addr_setup); + +/* Allocated/assigned physical address for shared memory */ +static phys_addr_t mk_phys_addr_base; + +/* Resource structure for tracking the memory in /proc/iomem */ +static struct resource mk_mem_res __ro_after_init = { + .name = "Multikernel Shared Memory", + .flags = IORESOURCE_MEM | IORESOURCE_BUSY, +}; + +/* Shared memory structures */ +struct mk_shared_data { + struct mk_ipi_data cpu_data[NR_CPUS]; /* Data area for each CPU */ +}; + +/* Pointer to the shared memory area (remapped virtual address) */ +static struct mk_shared_data *mk_shared_mem; + +/* Callback management */ +static struct mk_ipi_handler *mk_handlers; +static raw_spinlock_t mk_handlers_lock = __RAW_SPIN_LOCK_UNLOCKED(mk_handlers_lock); + +static void handler_work(struct irq_work *work) +{ + struct mk_ipi_handler *handler = container_of(work, struct mk_ipi_handler, work); + if (handler->callback) + handler->callback(handler->saved_data, handler->context); +} + +/** + * multikernel_register_handler - Register a callback for multikernel IPI + * @callback: Function to call when IPI is received + * @ctx: Context pointer passed to the callback + * + * Returns pointer to handler on success, NULL on failure + */ +struct mk_ipi_handler *multikernel_register_handler(mk_ipi_callback_t callback, void *ctx) +{ + struct mk_ipi_handler *handler; + unsigned long flags; + + if (!callback) + return NULL; + + handler = kzalloc(sizeof(*handler), GFP_KERNEL); + if (!handler) + return NULL; + + handler->callback = callback; + handler->context = ctx; + + init_irq_work(&handler->work, handler_work); + + raw_spin_lock_irqsave(&mk_handlers_lock, flags); + handler->next = mk_handlers; + mk_handlers = handler; + raw_spin_unlock_irqrestore(&mk_handlers_lock, flags); + + return handler; +} +EXPORT_SYMBOL(multikernel_register_handler); + +/** + * multikernel_unregister_handler - Unregister a multikernel IPI callback + * @handler: Handler pointer returned from multikernel_register_handler + */ +void multikernel_unregister_handler(struct mk_ipi_handler *handler) +{ + struct mk_ipi_handler **pp, *p; + unsigned long flags; + + if (!handler) + return; + + raw_spin_lock_irqsave(&mk_handlers_lock, flags); + pp = &mk_handlers; + while ((p = *pp) != NULL) { + if (p == handler) { + *pp = p->next; + break; + } + pp = &p->next; + } + raw_spin_unlock_irqrestore(&mk_handlers_lock, flags); + + /* Wait for pending work to complete */ + irq_work_sync(&handler->work); + kfree(p); +} +EXPORT_SYMBOL(multikernel_unregister_handler); + +/** + * multikernel_send_ipi_data - Send data to another CPU via IPI + * @cpu: Target CPU + * @data: Pointer to data to send + * @data_size: Size of data + * @type: User-defined type identifier + * + * This function copies the data to per-CPU storage and sends an IPI + * to the target CPU. + * + * Returns 0 on success, negative error code on failure + */ +int multikernel_send_ipi_data(int cpu, void *data, size_t data_size, unsigned long type) +{ + struct mk_ipi_data *target; + + if (cpu < 0 || cpu >= nr_cpu_ids) + return -EINVAL; + + if (data_size > MK_MAX_DATA_SIZE) + return -EINVAL; /* Data too large for buffer */ + + /* Ensure shared memory is initialized */ + if (!mk_shared_mem) + return -ENOMEM; + + /* Get target CPU's data area from shared memory */ + target = &mk_shared_mem->cpu_data[cpu]; + + /* Set header information */ + target->data_size = data_size; + target->sender_cpu = smp_processor_id(); + target->type = type; + + /* Copy the actual data into the buffer */ + if (data && data_size > 0) + memcpy(target->buffer, data, data_size); + + /* Send IPI to target CPU */ + __apic_send_IPI(cpu, MULTIKERNEL_VECTOR); + + return 0; +} +EXPORT_SYMBOL(multikernel_send_ipi_data); + +/** + * multikernel_interrupt_handler - Handle the multikernel IPI + * + * This function is called when a multikernel IPI is received. + * It invokes all registered callbacks with the per-CPU data. + */ +static void multikernel_interrupt_handler(void) +{ + struct mk_ipi_data *data; + struct mk_ipi_handler *handler; + int current_cpu = smp_processor_id(); + + /* Ensure shared memory is initialized */ + if (!mk_shared_mem) { + pr_err("Multikernel IPI received but shared memory not initialized\n"); + return; + } + + /* Get this CPU's data area from shared memory */ + data = &mk_shared_mem->cpu_data[current_cpu]; + + pr_debug("Multikernel IPI received on CPU %d from CPU %d, type=%u\n", + current_cpu, data->sender_cpu, data->type); + + raw_spin_lock(&mk_handlers_lock); + for (handler = mk_handlers; handler; handler = handler->next) { + handler->saved_data = data; + irq_work_queue(&handler->work); + } + raw_spin_unlock(&mk_handlers_lock); +} + +/** + * Generic multikernel interrupt handler - called by the IPI vector + * + * This is the function that gets called by the IPI vector handler. + */ +void generic_multikernel_interrupt(void) +{ + multikernel_interrupt_handler(); +} + +/** + * setup_shared_memory - Initialize shared memory for inter-kernel communication + * + * Maps a fixed physical memory region for sharing IPI data between kernels + * Returns 0 on success, negative error code on failure + */ +static int __init setup_shared_memory(void) +{ + /* Check if a fixed physical address was provided via parameter */ + if (mk_phys_addr_param) { + /* Use the provided physical address */ + mk_phys_addr_base = (phys_addr_t)mk_phys_addr_param; + pr_info("Using specified physical address 0x%llx for multikernel shared memory\n", + (unsigned long long)mk_phys_addr_base); + } else { + /* Dynamically allocate contiguous physical memory using memblock */ + mk_phys_addr_base = memblock_phys_alloc(MK_MEM_SIZE, PAGE_SIZE); + if (!mk_phys_addr_base) { + pr_err("Failed to allocate physical memory for multikernel IPI data\n"); + return -ENOMEM; + } + } + + /* Map the physical memory region to virtual address space */ + mk_shared_mem = memremap(mk_phys_addr_base, MK_MEM_SIZE, MEMREMAP_WB); + if (!mk_shared_mem) { + pr_err("Failed to map shared memory at 0x%llx for multikernel IPI data\n", + (unsigned long long)mk_phys_addr_base); + + /* Only free the memory if we allocated it dynamically */ + if (!mk_phys_addr_param) + memblock_phys_free(mk_phys_addr_base, MK_MEM_SIZE); + return -ENOMEM; + } + + /* Initialize the memory to zero */ + memset(mk_shared_mem, 0, sizeof(struct mk_shared_data)); + + pr_info("Allocated and mapped multikernel shared memory: phys=0x%llx, virt=%px, size=%lu bytes\n", + (unsigned long long)mk_phys_addr_base, mk_shared_mem, MK_MEM_SIZE); + + return 0; +} + +int __init multikernel_init(void) +{ + int ret; + + ret = setup_shared_memory(); + if (ret < 0) + return ret; + + pr_info("Multikernel IPI support initialized\n"); + return 0; +} + +static int __init init_shared_memory(void) +{ + /* Set up resource structure for /proc/iomem visibility */ + mk_mem_res.start = mk_phys_addr_base; + mk_mem_res.end = mk_phys_addr_base + MK_MEM_SIZE - 1; + + /* Register the resource in the global resource tree */ + if (insert_resource(&iomem_resource, &mk_mem_res)) { + pr_warn("Could not register multikernel shared memory region in resource tracking\n"); + /* Continue anyway as this is not fatal */ + return -1; + } + + pr_info("Registered multikernel shared memory in resource tree: 0x%llx-0x%llx\n", + (unsigned long long)mk_mem_res.start, (unsigned long long)mk_mem_res.end); + return 0; +} +core_initcall(init_shared_memory); + +/* ---- Flexible shared memory APIs (PFN-based) ---- */ +#define MK_PFN_IPI_TYPE 0x80000001U + +/* Send a PFN to another kernel via mk_ipi_data */ +int mk_send_pfn(int target_cpu, unsigned long pfn) +{ + return multikernel_send_ipi_data(target_cpu, &pfn, sizeof(pfn), MK_PFN_IPI_TYPE); +} + +/* Receive a PFN from mk_ipi_data. Caller must check type. */ +int mk_receive_pfn(struct mk_ipi_data *data, unsigned long *out_pfn) +{ + if (!data || !out_pfn) + return -EINVAL; + if (data->type != MK_PFN_IPI_TYPE || data->data_size != sizeof(unsigned long)) + return -EINVAL; + *out_pfn = *(unsigned long *)data->buffer; + return 0; +} + +void *mk_receive_map_page(struct mk_ipi_data *data) +{ + unsigned long pfn; + int ret; + + ret = mk_receive_pfn(data, &pfn); + if (ret < 0) + return NULL; + return memremap(pfn << PAGE_SHIFT, PAGE_SIZE, MEMREMAP_WB); +} -- 2.34.1
