Help with Linux APIC Features

Question

I am trying to play with local APIC features in the Linux kernel 2.6.32.40, but I am having some problems. I want to try sending Non-Maskable Interrupts (NMI) to all the processors on my system (I use Intel i7 Q740). I first read the documentation in the Intel Software Developer Manual Volume 3 on APIC features. It states that interrupts can be sent to all processors using the interrupt instruction register (ICR) located at 0xFEE00300. So I wrote a kernel module with the following init function to try and write to this register:

#include <linux/init.h> #include <linux/module.h> #include <linux/fs.h> MODULE_LICENSE("GPL"); #define SUCCESS 0 #define ICR_ADDRESS 0xFEE00300 #define ICR_PROGRAM 0x000C4C89 static int icr_init(void){ int * ICR = (int *)ICR_ADDRESS; printk(KERN_ALERT "Programing ICR\n"); *ICR = ICR_PROGRAM; return SUCCESS; } static void icr_exit(void){ printk(KERN_ALERT "Removing ICR Programing module removed"); } module_init(icr_init); module_exit(icr_exit); 

However, when I insert this module, the kernel crashes and complains that it cannot process the swap request @address 00000000fee00300. If you look in / proc / iomem, I can see that this address is in the range marked as "reserved"

 fee00000-fee00fff : reserved 

I also tried using the following functions:

 static inline void __default_local_send_IPI_allbutself(int vector) 

but the kernel still throws the message "unable to process search requests" and crashes. Anyone have any suggestions? Why is this memory range marked as “reserved” and not marked as used by the local APIC? Thanks in advance.

Answer 1

The APIC address is a physical memory address, but you are trying to access it as a linear memory address - why your first approach does not work. The memory is marked as “reserved” precisely because it belongs to APIC, not real memory.

You must use the internal functions of the kernel. To do this, you must include <asm/apic.h> and use:

 apic->send_IPI_allbutself(vector);