From: Cong Wang <[email protected]> This patch extends the kexec subsystem to support multikernel functionality, allowing different kernel instances to be loaded and executed on specific CPUs. The implementation introduces:
- New KEXEC_TYPE_MULTIKERNEL type and KEXEC_MULTIKERNEL flag - multikernel_kick_ap() function for CPU-specific kernel booting - LINUX_REBOOT_CMD_MULTIKERNEL reboot command with CPU parameter - Specialized segment loading for multikernel images using memremap - Integration with existing kexec infrastructure while bypassing standard machine_kexec_prepare() for avoiding resets The multikernel_kexec() function validates CPU availability and uses the existing kexec image start address to boot the target CPU with a different kernel instance. This enables heterogeneous computing scenarios where different CPUs can run specialized kernel variants. Signed-off-by: Cong Wang <[email protected]> --- arch/x86/include/asm/smp.h | 1 + arch/x86/kernel/smpboot.c | 104 ++++++++++++++++++++++++++++++++++ include/linux/kexec.h | 6 +- include/uapi/linux/kexec.h | 1 + include/uapi/linux/reboot.h | 2 +- kernel/kexec_core.c | 109 ++++++++++++++++++++++++++++++++++++ kernel/reboot.c | 10 ++++ 7 files changed, 230 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index 22bfebe6776d..1a59fd0de759 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -107,6 +107,7 @@ void native_smp_prepare_cpus(unsigned int max_cpus); void native_smp_cpus_done(unsigned int max_cpus); int common_cpu_up(unsigned int cpunum, struct task_struct *tidle); int native_kick_ap(unsigned int cpu, struct task_struct *tidle); +int multikernel_kick_ap(unsigned int cpu, unsigned long kernel_start_address); int native_cpu_disable(void); void __noreturn hlt_play_dead(void); void native_play_dead(void); diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index eb289abece23..7b27fdc1d169 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -833,6 +833,72 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle) return 0; } +// must be locked by cpus_read_lock() +static int do_multikernel_boot_cpu(u32 apicid, int cpu, unsigned long kernel_start_address) +{ + unsigned long start_ip = real_mode_header->trampoline_start; + int ret; + + pr_info("do_multikernel_boot_cpu(apicid=%u, cpu=%u, kernel_start_address=%lx)\n", apicid, cpu, kernel_start_address); +#ifdef CONFIG_X86_64 + /* If 64-bit wakeup method exists, use the 64-bit mode trampoline IP */ + if (apic->wakeup_secondary_cpu_64) + start_ip = real_mode_header->trampoline_start64; +#endif + //initial_code = (unsigned long)start_secondary; + initial_code = (unsigned long)kernel_start_address; + + if (IS_ENABLED(CONFIG_X86_32)) { + early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(cpu); + //initial_stack = idle->thread.sp; + } else if (!(smpboot_control & STARTUP_PARALLEL_MASK)) { + smpboot_control = cpu; + } + + /* Skip init_espfix_ap(cpu); */ + + /* Skip announce_cpu(cpu, apicid); */ + + /* + * This grunge runs the startup process for + * the targeted processor. + */ + if (x86_platform.legacy.warm_reset) { + + pr_debug("Setting warm reset code and vector.\n"); + + smpboot_setup_warm_reset_vector(start_ip); + /* + * Be paranoid about clearing APIC errors. + */ + if (APIC_INTEGRATED(boot_cpu_apic_version)) { + apic_write(APIC_ESR, 0); + apic_read(APIC_ESR); + } + } + + smp_mb(); + + /* + * Wake up a CPU in difference cases: + * - Use a method from the APIC driver if one defined, with wakeup + * straight to 64-bit mode preferred over wakeup to RM. + * Otherwise, + * - Use an INIT boot APIC message + */ + if (apic->wakeup_secondary_cpu_64) + ret = apic->wakeup_secondary_cpu_64(apicid, start_ip, cpu); + else if (apic->wakeup_secondary_cpu) + ret = apic->wakeup_secondary_cpu(apicid, start_ip, cpu); + else + ret = wakeup_secondary_cpu_via_init(apicid, start_ip, cpu); + + pr_info("do_multikernel_boot_cpu end\n"); + /* If the wakeup mechanism failed, cleanup the warm reset vector */ + if (ret) + arch_cpuhp_cleanup_kick_cpu(cpu); + return ret; +} /* * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad * (ie clustered apic addressing mode), this is a LOGICAL apic ID. @@ -905,6 +971,44 @@ static int do_boot_cpu(u32 apicid, unsigned int cpu, struct task_struct *idle) return ret; } +// must be locked by cpus_read_lock() +int multikernel_kick_ap(unsigned int cpu, unsigned long kernel_start_address) +{ + u32 apicid = apic->cpu_present_to_apicid(cpu); + int err; + + lockdep_assert_irqs_enabled(); + + pr_info("++++++++++++++++++++=_---CPU UP %u\n", cpu); + + if (apicid == BAD_APICID || !apic_id_valid(apicid)) { + pr_err("CPU %u has invalid APIC ID %x. Aborting bringup\n", cpu, apicid); + return -EINVAL; + } + + if (!test_bit(apicid, phys_cpu_present_map)) { + pr_err("CPU %u APIC ID %x is not present. Aborting bringup\n", cpu, apicid); + return -EINVAL; + } + + /* + * Save current MTRR state in case it was changed since early boot + * (e.g. by the ACPI SMI) to initialize new CPUs with MTRRs in sync: + */ + mtrr_save_state(); + + /* the FPU context is blank, nobody can own it */ + per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL; + /* skip common_cpu_up(cpu, tidle); */ + + err = do_multikernel_boot_cpu(apicid, cpu, kernel_start_address); + if (err) + pr_err("do_multikernel_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu); + + return err; +} + + int native_kick_ap(unsigned int cpu, struct task_struct *tidle) { u32 apicid = apic->cpu_present_to_apicid(cpu); diff --git a/include/linux/kexec.h b/include/linux/kexec.h index ff7e231b0485..edf64bc98ed5 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -358,9 +358,10 @@ struct kimage { unsigned long control_page; /* Flags to indicate special processing */ - unsigned int type : 1; + unsigned int type : 2; #define KEXEC_TYPE_DEFAULT 0 #define KEXEC_TYPE_CRASH 1 +#define KEXEC_TYPE_MULTIKERNEL 2 unsigned int preserve_context : 1; /* If set, we are using file mode kexec syscall */ unsigned int file_mode:1; @@ -437,6 +438,7 @@ extern void machine_kexec(struct kimage *image); extern int machine_kexec_prepare(struct kimage *image); extern void machine_kexec_cleanup(struct kimage *image); extern int kernel_kexec(void); +extern int multikernel_kexec(int cpu); extern struct page *kimage_alloc_control_pages(struct kimage *image, unsigned int order); @@ -458,7 +460,7 @@ bool kexec_load_permitted(int kexec_image_type); #define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR | KEXEC_CRASH_HOTPLUG_SUPPORT) #else #define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR | \ - KEXEC_CRASH_HOTPLUG_SUPPORT) + KEXEC_CRASH_HOTPLUG_SUPPORT | KEXEC_MULTIKERNEL) #endif /* List of defined/legal kexec file flags */ diff --git a/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h index 55749cb0b81d..346e0ff4e663 100644 --- a/include/uapi/linux/kexec.h +++ b/include/uapi/linux/kexec.h @@ -14,6 +14,7 @@ #define KEXEC_PRESERVE_CONTEXT 0x00000002 #define KEXEC_UPDATE_ELFCOREHDR 0x00000004 #define KEXEC_CRASH_HOTPLUG_SUPPORT 0x00000008 +#define KEXEC_MULTIKERNEL 0x00000010 #define KEXEC_ARCH_MASK 0xffff0000 /* diff --git a/include/uapi/linux/reboot.h b/include/uapi/linux/reboot.h index 58e64398efc5..aac2f2f94a98 100644 --- a/include/uapi/linux/reboot.h +++ b/include/uapi/linux/reboot.h @@ -34,7 +34,7 @@ #define LINUX_REBOOT_CMD_RESTART2 0xA1B2C3D4 #define LINUX_REBOOT_CMD_SW_SUSPEND 0xD000FCE2 #define LINUX_REBOOT_CMD_KEXEC 0x45584543 - +#define LINUX_REBOOT_CMD_MULTIKERNEL 0x4D4B4C49 #endif /* _UAPI_LINUX_REBOOT_H */ diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index fa00b239c5d9..7d89d00e2cde 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -41,6 +41,7 @@ #include <linux/objtool.h> #include <linux/kmsg_dump.h> #include <linux/dma-map-ops.h> +#include <linux/memblock.h> #include <asm/page.h> #include <asm/sections.h> @@ -942,6 +943,84 @@ static int kimage_load_crash_segment(struct kimage *image, int idx) } #endif +static int kimage_load_multikernel_segment(struct kimage *image, int idx) +{ + /* For multikernel we simply copy the data from + * user space to it's destination. + * We do things a page at a time for the sake of kmap. + */ + struct kexec_segment *segment = &image->segment[idx]; + unsigned long maddr; + size_t ubytes, mbytes; + int result; + unsigned char __user *buf = NULL; + unsigned char *kbuf = NULL; + + result = 0; + if (image->file_mode) + kbuf = segment->kbuf; + else + buf = segment->buf; + ubytes = segment->bufsz; + mbytes = segment->memsz; + maddr = segment->mem; + pr_info("Loading multikernel segment: mem=0x%lx, memsz=0x%zu, buf=0x%px, bufsz=0x%zu\n", + maddr, mbytes, buf, ubytes); + while (mbytes) { + char *ptr; + size_t uchunk, mchunk; + unsigned long page_addr = maddr & PAGE_MASK; + unsigned long page_offset = maddr & ~PAGE_MASK; + + /* Use memremap to map the physical address */ + ptr = memremap(page_addr, PAGE_SIZE, MEMREMAP_WB); + if (!ptr) { + pr_err("Failed to memremap memory at 0x%lx\n", page_addr); + result = -ENOMEM; + goto out; + } + + /* Adjust pointer to the offset within the page */ + ptr += page_offset; + + /* Calculate chunk sizes */ + mchunk = min_t(size_t, mbytes, PAGE_SIZE - page_offset); + uchunk = min(ubytes, mchunk); + + /* Zero the trailing part of the page if needed */ + if (mchunk > uchunk) { + /* Zero the trailing part of the page */ + memset(ptr + uchunk, 0, mchunk - uchunk); + } + + if (uchunk) { + /* For file based kexec, source pages are in kernel memory */ + if (image->file_mode) + memcpy(ptr, kbuf, uchunk); + else + result = copy_from_user(ptr, buf, uchunk); + ubytes -= uchunk; + if (image->file_mode) + kbuf += uchunk; + else + buf += uchunk; + } + + /* Clean up */ + memunmap(ptr - page_offset); + if (result) { + result = -EFAULT; + goto out; + } + maddr += mchunk; + mbytes -= mchunk; + + cond_resched(); + } +out: + return result; +} + int kimage_load_segment(struct kimage *image, int idx) { int result = -ENOMEM; @@ -955,6 +1034,9 @@ int kimage_load_segment(struct kimage *image, int idx) result = kimage_load_crash_segment(image, idx); break; #endif + case KEXEC_TYPE_MULTIKERNEL: + result = kimage_load_multikernel_segment(image, idx); + break; } return result; @@ -1229,3 +1311,30 @@ int kernel_kexec(void) kexec_unlock(); return error; } + +int multikernel_kexec(int cpu) +{ + int rc; + + pr_info("multikernel kexec: cpu %d\n", cpu); + + if (cpu_online(cpu)) { + pr_err("The CPU is currently running with this kernel instance."); + return -EBUSY; + } + + if (!kexec_trylock()) + return -EBUSY; + if (!kexec_image) { + rc = -EINVAL; + goto unlock; + } + + cpus_read_lock(); + rc = multikernel_kick_ap(cpu, kexec_image->start); + cpus_read_unlock(); + +unlock: + kexec_unlock(); + return rc; +} diff --git a/kernel/reboot.c b/kernel/reboot.c index ec087827c85c..f3ac703c4695 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -717,6 +717,10 @@ EXPORT_SYMBOL_GPL(kernel_power_off); DEFINE_MUTEX(system_transition_mutex); +struct multikernel_boot_args { + int cpu; +}; + /* * Reboot system call: for obvious reasons only root may call it, * and even root needs to set up some magic numbers in the registers @@ -729,6 +733,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd, void __user *, arg) { struct pid_namespace *pid_ns = task_active_pid_ns(current); + struct multikernel_boot_args boot_args; char buffer[256]; int ret = 0; @@ -799,6 +804,11 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd, case LINUX_REBOOT_CMD_KEXEC: ret = kernel_kexec(); break; + case LINUX_REBOOT_CMD_MULTIKERNEL: + if (copy_from_user(&boot_args, arg, sizeof(boot_args))) + return -EFAULT; + ret = multikernel_kexec(boot_args.cpu); + break; #endif #ifdef CONFIG_HIBERNATION -- 2.34.1
